status of meson spectroscopy in the pdg · 2021. 8. 1. · 971.1± 4.0 28 aguilar-... 91 ehs 400 pp...

1

Status of Meson Spectroscopy in the PDGHadron 2021 Roundtable

July 30, 2021Ryan Mitchell (Indiana University)

“Unstable Mesons” are curated by the PDG Meson Team:

Simon Eidelman (Novosibirsk)Claude Amsler (Vienna)Michael Doser (CERN)Thomas Gutsche (Tübingen)Christoph Hanhart (Jülich)Juan-Jose Hernández-Rey (Valencia)Carlos Lourenço (CERN)Alberto Masoni (Cagliari)Ryan Mitchell (Indiana)Mikhail Mikhasenko (CERN)Sergio Navas (Granada)Claudia Patrignani (Bologna)Stefan Spanier (Tennessee)Graziano Venanzoni (Pisa)Vitaly Vorobyev (Novosibirsk)

Philosophy: descriptive vs. prescriptive (generally descriptive)

descriptive: maintain listings and reviews

prescriptive: collect standards (e.g. naming scheme) and best practices (e.g. moving beyond BW parameters)

A few notes:

1. Theory papers are being incorporated into the listings.

2. The listings are rapidly expanding.

sometimes changes are provisional

the naming scheme is expanding

reviews are undergoing major revisions

⟹⟹⟹

Send ideas/feedback/mistakes to anyone on the list or to [email protected]

mailto:[email protected]

2








A few notes:






⟹⟹⟹


Citation: P.A. Zyla et al. (Particle Data Group), Prog. Theor. Exp. Phys. 2020, 083C01 (2020) and 2021 update

π1(1600) IG (JPC ) = 1−(1−+)

See the review on ”Non-qq Mesons” and a note in PDG 06, Journalof Physics G33G33G33G33 1 (2006).

π1(1600) T-Matrix Pole√

sπ1(1600) T-Matrix Pole√



s

VALUE (MeV) DOCUMENT ID TECN COMMENT

(1564 ± 24 ± 86) − i (246 ±

27 ± 51)

1 RODAS 19 JPAC 191 π− p → η(′)π− p

1The coupled-channel analysis of both the ηπ and η′π systems using ADOLPH 15 data.

π1(1600) MASSπ1(1600) MASSπ1(1600) MASSπ1(1600) MASS

VALUE (MeV) EVTS DOCUMENT ID TECN COMMENT

1661+ 15− 11 OUR AVERAGE1661+ 15− 11 OUR AVERAGE1661+ 15− 11 OUR AVERAGE1661+ 15− 11 OUR AVERAGE Error includes scale factor of 1.2.

1600+110− 60 46M 1 AGHASYAN 18B COMP 190 π− p → π−π+π−p

1664± 8±10 145k 2 LU 05 B852 18 π−p → ωπ−π0 p

1709± 24±41 69k 3 KUHN 04 B852 18 π−p → ηπ+π−π− p

1597± 10+45−10

3 IVANOV 01 B852 18 π−p → η′π− p

• • • We do not use the following data for averages, fits, limits, etc. • • •

1660± 10+ 0−64 420k 4 ALEKSEEV 10 COMP 190 π−Pb → π−π−π+Pb′

1593± 8+29−47

3,5 ADAMS 98B B852 18.3 π− p → π+π−π− p

1 Statistical error negligible.2May be a different state: natural and unnatural parity exchanges.3Natural parity exchange.4 Superseded by AGHASYAN 2018B.5 Superseded by DZIERBA 06 excluding this state in a more refined PWA analysis, with

2.6 M events of π−p → π−π−π+ p and 3 M events of π− p → π−π0π0p of E852data.

π1(1600) WIDTHπ1(1600) WIDTHπ1(1600) WIDTHπ1(1600) WIDTH


240± 50 OUR AVERAGE240± 50 OUR AVERAGE240± 50 OUR AVERAGE240± 50 OUR AVERAGE Error includes scale factor of 1.7. See the ideogram below.

580+100−230 46M 1 AGHASYAN 18B COMP 190 π− p → π−π+π−p

185± 25± 28 145k 2 LU 05 B852 18 π−p → ωπ−π0 p

403± 80±115 69k 3 KUHN 04 B852 18 π−p → ηπ+π−π− p

340± 40± 50 3 IVANOV 01 B852 18 π−p → η′π− p


269± 21+ 42− 64 420k 4 ALEKSEEV 10 COMP 190 π−Pb → π−π−π+Pb′

168± 20+150− 12

3,5 ADAMS 98B B852 18.3 π− p → π+π−π− p

https://pdg.lbl.gov Page 1 Created: 6/1/2021 08:31


3








A few notes:






⟹⟹⟹



f0(980) IG (JPC ) = 0+(0 + +)

See the review on ”Scalar Mesons below 2 GeV.”

f0(980) T-MATRIX POLE√

sf0(980) T-MATRIX POLE√



s

VALUE (MeV) DOCUMENT ID TECN COMMENT


(1003+ 5−27) − i(21+10

− 8)1 GARCIA-MAR...11 RVUE Compilation

(996 ± 7) − i(25+10− 6)

2 GARCIA-MAR...11 RVUE Compilation

(973+ 39−127) − i(11+189

− 11)3 PELAEZ 04A RVUE ππ → ππ

1Reanalysis of the Ke4 data of BATLEY 10C and the πN → ππN data of HYAMS 73,GRAYER 74, and PROTOPOPESCU 73 using Roy equations.

2 Reanalysis of the Ke4 data of BATLEY 10C and the πN → ππN data of HYAMS 73,GRAYER 74, and PROTOPOPESCU 73 using GKPY equations.

3 Reanalysis of data from PROTOPOPESCU 73, ESTABROOKS 74, GRAYER 74, andCOHEN 80 in the unitarized ChPT model.

f0(980) MASSf0(980) MASSf0(980) MASSf0(980) MASS


990 ±20 OUR ESTIMATE990 ±20 OUR ESTIMATE990 ±20 OUR ESTIMATE990 ±20 OUR ESTIMATE


992.8± 0.8± 1.0 1 ALBRECHT 20 RVUE 0.9 pp → π0π0 η,

π0ηη, π0K+K−

992.0+ 8.5− 7.5± 8.6 2 AAIJ 19H LHCB pp → D±X

989.4± 1.3 424 ABLIKIM 15P BES3 J/ψ → K+K− 3π989.9± 0.4 706 ABLIKIM 12E BES3 J/ψ → γ 3π

996 + 4−14

3 MOUSSALLAM11 RVUE Compilation

981 ±43 4 MENNESSIER 10 RVUE Compilation

1030 +30−10

5 ANISOVICH 09 RVUE 0.0 pp, πN

977 +11− 9 ± 1 44 6 ECKLUND 09 CLEO 4.17 e+ e− →

D−sD∗+s

+ c.c.

982.2± 1.0+ 8.1− 8.0

7 UEHARA 08A BELL 10.6 e+ e− →e+ e−π0π0

976.8± 0.3+10.1− 0.6 64k 8 AMBROSINO 07 KLOE 1.02 e+ e− → π0π0γ

984.7± 0.4+ 2.4− 3.7 64k 9 AMBROSINO 07 KLOE 1.02 e+ e− → π0π0γ

973 ± 3 262± 30 10 AUBERT 07AKBABR 10.6 e+ e− →φπ+π−γ

970 ± 7 54 ± 9 10 AUBERT 07AKBABR 10.6 e+ e− →φπ0π0γ

953 ±20 2.6k 11 BONVICINI 07 CLEO D+ → π−π+π+

985.6+ 1.2− 1.5

+ 1.1− 1.6

12 MORI 07 BELL 10.6 e+ e− →e+ e−π+π−



988 ±10 39 MORGAN 93 RVUE ππ (K K) → ππ (K K),J/ψ → φππ (K K),Ds → π (ππ)

971.1± 4.0 28 AGUILAR-... 91 EHS 400 pp

979 ± 4 40 ARMSTRONG 91 OMEG 300 pp → ppππ ,ppK K

956 ±12 BREAKSTONE90 SFM pp → ppπ+π−

959.4± 6.5 28 AUGUSTIN 89 DM2 J/ψ → ωπ+π−

978 ± 9 28 ABACHI 86B HRS e+ e− → π+π−X

985.0+ 9.0−39.0 ETKIN 82B MPS 23 π− p → n2K0

S

974 ± 4 40 GIDAL 81 MRK2 J/ψ → π+π−X975 41 ACHASOV 80 RVUE

986 ±10 40 AGUILAR-... 78 HBC 0.7 pp → K0SK0S

969 ± 5 40 LEEPER 77 ASPK 2–2.4 π− p →

π+π− n , K+K− n987 ± 7 40 BINNIE 73 CNTR π− p → nMM

1012 ± 6 42 GRAYER 73 ASPK 17 π− p → π+π− n

1007 ±20 42 HYAMS 73 ASPK 17 π− p → π+π− n

997 ± 6 42 PROTOPOP... 73 HBC 7 π+p → π+ pπ+π−

1T-matrix pole, 5 poles, 5 channels, including scattering data from HYAMS 75 (ππ),

LONGACRE 86 (K K), BINON 83 (ηη), and BINON 84C (ηη′). Second solution 977.8±0.6 ± 1.6 MeV.

2 From the D± → K±K+K− Dalitz plot fit with the Triple-M amplitude in the multi-meson model of AOUDE 18.

3Pole position. Used Roy equations.4Average of the analyses of three data sets in the K-matrix model. Uses the data ofBATLEY 08A, HYAMS 73, and GRAYER 74, partially of COHEN 80 or ETKIN 82B.

5On sheet II in a 2-pole solution. The other pole is found on sheet III at (850−100i) MeV6Using a relativistic Breit-Wigner function and taking into account the finite Ds mass.7Breit-Wigner mass. Using finite width corrections according to FLATTE 76 andACHASOV 05, and the ratio gf0K K /gf0ππ

= 0.

8 In the kaon-loop fit.9 In the no-structure fit.

10 Systematic errors not estimated.11 FLATTE 76 parameterization. gf0ππ

= 329± 96 MeV/c2 assuming gf0KK

/gf0ππ=2.

12Breit-Wigner mass. Using finite width corrections according to FLATTE 76 andACHASOV 05, and the ratio gf0K K /gf0ππ

= 4.21 ± 0.25 ± 0.21 from ABLIKIM 05.

13 In the kaon-loop fit following formalism of ACHASOV 89.14 In the no-structure fit assuming a direct coupling of φ to f0 γ.15 FLATTE 76 parameterization. Supersedes GARMASH 05.16 FLATTE 76 parameterization, g

f0K K/gf0ππ

= 4.21 ± 0.25 ± 0.21.

17K-matrix pole from combined analysis of π− p → π0π0n, π− p → K K n,

π+π− → π+π−, pp → π0π0π0, π0ηη, π0π0η, π+π−π0, K+K−π0, K0SK0Sπ0,

K+K0Sπ− at rest, pn → π−π−π+, K0

SK−π0, K0

SK0Sπ− at rest.

18 From the negative interference with the f0(500) meson of AITALA 01B using theACHASOV 89 parameterization for the f0(980), a Breit-Wigner for the f0(500), andACHASOV 01F for the ρπ contribution.

19Coupled-channel Breit-Wigner, couplings gπ=0.09±0.01±0.01, gK=0.02±0.04±0.03.20 Supersedes ACHASOV 98I. Using the model of ACHASOV 89.

https://pdg.lbl.gov Created: 6/1/2021 08:30


4








A few notes:






⟹⟹⟹


91. Charmonium system 1

91. Charmonium System

Updated in 2012.

= PCJ − +0 − −1 + +0 + +1+ −1 + +2

(2S) cη

(1S) cη

(2S)ψ

(4660)X

(4360)X

(4260)X

(4415)ψ

(4160)ψ

(4040)ψ

(3770)ψ

(1S) ψ/J

(1P) ch

(1P) c2

χ

(2P) c2

χ(3872)X

?)-+(2

(1P) c1

χ(1P)

c0χ

0π

π π

η

0π

π πη

π π

π π

π π

π π

Thresholds:

DD

*D DsD sD*D*DsD*sD

*sD*sD

2900

3100

3300

3500

3700

3900

4100

4300

4500

4700

Mass (MeV)

The level scheme of the cc states showing experimentally established states with solidlines. Singlet states are called ηc and hc, triplet states ψ and χcJ , and unassignedcharmonium-like states X . In parentheses it is sufficient to give the radial quantumnumber and the orbital angular momentum to specify the states with all their quantumnumbers. Only observed hadronic transitions are shown; the single photon transitionsψ(nS) → γηc(mP ), ψ(nS) → γχcJ (mP ), and χcJ (1P ) → γJ/ψ are omitted for clarity.

M. Tanabashi et al. (Particle Data Group), Phys. Rev. D 98, 030001 (2018)June 5, 2018 20:06


5








A few notes:






⟹⟹⟹


Charmonium system 1

Charmonium System

Updated August 2019.

= PCJ − +0 − −1 + +0 + +1+ −1 + +2 − −2 − −3

(2S) cη

(1S) cη

(2S)ψ

(4660)ψ

(4360)ψ

(4260)ψ

(4415)ψ

(4160)ψ

(4040)ψ

(3770)ψ

(1S) ψ/J

(1P) ch

(1P) c2

χ

(3930) c2

χ(3872)

c1χ

(1P) c1

χ

(1P) c0

χ

(3823)2

ψ

(3915) X?]++[2

(4140)c1

χ

(4274)c1

χ

(4430) cZ

(4020) X

(3900) cZ

(3860)c0

χ

(4500)c0

χ

(4700)c0

χ

(4200) cZ(4230)ψ

(4390)ψ

(3842) 3

ψ

0π

π π

η

0π

π πη

π πKK

π π

π π

ω, π π

0ππ

π

π

ω

φ

Thresholds:

DD

*DD sD sD

*D *DsD *sD

*sD *sD

2900

3100

3300

3500

3700

3900

4100

4300

4500

4700

Mass (MeV)

The level scheme of meson states containing a minimal quark content of cc. The name ofa state is determined by its quantum numbers IGJPC (see the review “Naming Schemefor Hadrons”). States with unestablished quantum numbers are called X and are drawnaccording to our best estimate of their likely JPC . States included in the SummaryTables are shown with solid lines; selected states not in the Summary Tables, but withassigned quantum numbers, are shown with dotted lines. The arrows indicate the mostdominant hadronic transitions. Single photon transitions, including ψ(nS) → γηc(mS),ψ(nS) → γχcJ(1P ), and χcJ (1P ) → γJ/ψ, are omitted for clarity. For orientation, thelocation of the thresholds related to a pair of ground state open charm mesons is indicatedin the figure.

P.A. Zyla et al. (Particle Data Group), Prog. Theor. Exp. Phys. 2020, 083C01 (2020)June 1, 2020 08:27


6








A few notes:






⟹⟹⟹


Charmonium system 1

Charmonium System


= PCJ − +0 − −1 + +0 + +1+ −1 + +2 − −2 − −3

(2S) cη

(1S) cη

(2S)ψ

(4660)ψ

(4360)ψ

(4260)ψ

(4415)ψ

(4160)ψ

(4040)ψ

(3770)ψ

(1S) ψ/J

(1P) ch

(1P) c2

χ

(3930) c2

χ(3872)

c1χ

(1P) c1

χ

(1P) c0

χ

(3823)2

ψ

(3915) X?]++[2

(4140)c1

χ

(4274)c1

χ

(4430) cZ

(4020) X

(3900) cZ

(3860)c0

χ

(4500)c0

χ

(4700)c0

χ

(4200) cZ(4230)ψ

(4390)ψ

(3842) 3

ψ

0π

π π

η

0π

π πη

π πKK

π π

π π

ω, π π

0ππ

π

π

ω

φ

Thresholds:

DD

*DD sD sD

*D *DsD *sD

*sD *sD

2900

3100

3300

3500

3700

3900

4100

4300

4500

4700

Mass (MeV)



EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

CERN-EP-2021-025LHCb-PAPER-2020-044

March 2, 2021

Observation of new resonancesdecaying to J/ K+ and J/ �

LHCb collaboration†

Abstract

The first observation of exotic states with a new quark content ccus decaying to theJ/ K+ final state is reported with high significance from an amplitude analysis ofthe B+ ! J/ �K+ decay. The analysis is carried out using proton-proton collisiondata corresponding to a total integrated luminosity of 9 fb�1 collected by the LHCbexperiment at centre-of-mass energies of 7, 8 and 13TeV. The most significant state,Zcs(4000)+, has a mass of 4003 ± 6+ 4

� 14MeV, a width of 131 ± 15 ± 26MeV, andspin-parity JP = 1+, where the quoted uncertainties are statistical and systematic,respectively. A new 1+ X(4685) state decaying to the J/ � final state is alsoobserved with high significance. In addition, the four previously reported J/ �states are confirmed and two more exotic states, Zcs(4220)+ and X(4630), areobserved with significance exceeding five standard deviations.

Submitted to Phys. Rev. Lett.

© 2021 CERN for the benefit of the LHCb collaboration. CC BY 4.0 licence.

†Authors are listed at the end of this paper.ar

Xiv

:210

3.01

803v

1 [h

ep-e

x] 2

Mar

202

1

EUROPEAN

ORGANIZATIO

NFOR

NUCLEAR

RESEARCH

(CERN)

CERN-EP-2021-025

LHCb-PAPER-2020-044

March

2,2021

Observ

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nofnew

resonances

decay

ingto

J/

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andJ/ �

LHCbcollab

oration†

Abstra

ct

Thefirst

observation

ofexotic

stateswith

anew

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contentccu

sdecayin

gto

the

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+final

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reported

with

high

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cefrom

anam

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alysisof

theB

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+decay.

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correspon

dingto

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of9fb

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of7,

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.Themost

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state,Zcs (4000)

+,has

amass

of4003

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14MeV

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,an

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JP=

1+,where

thequ

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Submitted

toPhys.

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©2021

CERN

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BY

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†Authors

arelisted

attheendof

this

pap

er.

arXiv:2103.01803v1 [hep-ex] 2 Mar 2021

1.5 2

Can

dida

tes /

(10

MeV

)

100

200

300

400

500

600

700 (4630)X (4500)X

(4700)X NRX

(4140)X (4274)X

(4685)X (4150)X

(4000)csZ

(4220)csZ

LHCb

[GeV]+Kφm1.5 2

Can

dida

tes /

(10

MeV

)0

100

200

300

400

500

600

700 − 0K + 1K − 1K + 2K − 2K

Background

Total fit-1Data 9 fb

LHCb4.2 4.4 4.6 4.80

100

200

300

400

500

600

700LHCb

[GeV]φψJ/m4.2 4.4 4.6 4.8

0

100

200

300

400

500

600

700LHCb

3.6 3.8 4 4.2

100

200

300

400

500

600

700LHCb

[GeV]+KψJ/m3.6 3.8 4 4.2

0

100

200

300

400

500

600

700LHCb

Figure 3: Distributions of �K+ (left), J/ � (middle) and J/ K+ (right) invariant masses forthe B+ ! J/ �K+ candidates (black data points) compared with the fit results (red solid lines)of the default model (top row) and the Run 1 model (bottom row).

[GeV]+KψJ/m 3.8 4 4.2

Can

dida

tes /

(10

MeV

)

50

100

150

200

250

300

-1Data 9 fbTotal fit

fitcsZNo (4000)csZ

( 4.25, 4.35) GeV∈ φψJ/ m

LHCb

[GeV]+KψJ/m 3.8 4 4.2

50

100

150

200

250

300 ( 4.35, 4.45) GeV∈ φψJ/ m

Figure 4: Fit projections onto mJ/ K+ in two slices of mJ/ � for the default model with andwithout the 1+ Z+

cs states. The narrow Z+cs state at 4 GeV is evident.

Fig. 3 shows the invariant mass distributions for all pairs of final state particles ofthe B+ ! J/ �K+ decay with fit projections from the amplitude analysis overlaid, forboth the default model and the Run 1 model. The fit results are summarised in Table 1,including mass, width, fit fraction (FF), and significance of each component. The massesand widths of the four X states studied using the LHCb Run 1 sample only are consistentwith the previous measurements [14, 15]. The significance of each component is evaluatedby assuming that the change of twice the log-likelihood between the default fit and the fitwithout this component follows a �2 distribution. The corresponding number of degrees offreedom is equal to the reduction in the number of free parameters multiplied by a factor

5

B+ → J/ψϕK+

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

CERN-EP-2021-025LHCb-PAPER-2020-044

March 2, 2021

Observation of new resonancesdecaying to J/ K+ and J/ �

LHCb collaboration†

Abstract

The first observation of exotic states with a new quark content ccus decaying to theJ/ K+ final state is reported with high significance from an amplitude analysis ofthe B+ ! J/ �K+ decay. The analysis is carried out using proton-proton collisiondata corresponding to a total integrated luminosity of 9 fb�1 collected by the LHCbexperiment at centre-of-mass energies of 7, 8 and 13TeV. The most significant state,Zcs(4000)+, has a mass of 4003 ± 6+ 4

� 14MeV, a width of 131 ± 15 ± 26MeV, andspin-parity JP = 1+, where the quoted uncertainties are statistical and systematic,respectively. A new 1+ X(4685) state decaying to the J/ � final state is alsoobserved with high significance. In addition, the four previously reported J/ �states are confirmed and two more exotic states, Zcs(4220)+ and X(4630), areobserved with significance exceeding five standard deviations.

Submitted to Phys. Rev. Lett.

© 2021 CERN for the benefit of the LHCb collaboration. CC BY 4.0 licence.

†Authors are listed at the end of this paper.

arX

iv:2

103.

0180

3v1

[hep

-ex]

2 M

ar 2

021


7








A few notes:






⟹⟹⟹


Charmonium system 1

Charmonium System


= PCJ − +0 − −1 + +0 + +1+ −1 + +2 − −2 − −3

(2S) cη

(1S) cη

(2S)ψ

(4660)ψ

(4360)ψ

(4260)ψ

(4415)ψ

(4160)ψ

(4040)ψ

(3770)ψ

(1S) ψ/J

(1P) ch

(1P) c2

χ

(3930) c2

χ(3872)

c1χ

(1P) c1

χ

(1P) c0

χ

(3823)2

ψ

(3915) X?]++[2

(4140)c1

χ

(4274)c1

χ

(4430) cZ

(4020) X

(3900) cZ

(3860)c0

χ

(4500)c0

χ

(4700)c0

χ

(4200) cZ(4230)ψ

(4390)ψ

(3842) 3

ψ

0π

π π

η

0π

π πη

π πKK

π π

π π

ω, π π

0ππ

π

π

ω

φ

Thresholds:

DD

*DD sD sD

*D *DsD *sD

*sD *sD

2900

3100

3300

3500

3700

3900

4100

4300

4500

4700

Mass (MeV)



3700 3800 3900 4000 4100 4200 4300 4400 4500 4600 4700

Mass [MeV]

0

20

40

60

80

100

120

140

160

Wid

th

[MeV

]

StatesψPDG 2020

R peaksABLIKIM 08D (BESII) R

µµ K→AAIJ 13BC (LHCb) B (4230)ψ

c0χωABLIKIM 19AI (BESIII)

DD*πABLIKIM 19R (BESIII) X(3872)γABLIKIM 19V (BESIII)

ψJ/ππABLIKIM 17B (BESIII)

chππABLIKIM 17G (BESIII) (2S)ψππABLIKIM 17V (BESIII)

(4360)ψ

ψJ/ππABLIKIM 17B (BESIII) (2S)ψππABLIKIM 17V (BESIII)

(2S)ψππWANG 15A (BELLE) (2S)ψππLEES 14F (BABAR)

(4390)ψ

chππABLIKIM 17G (BESIII) (4660)ψ

s1Ds

JIA 19A (BELLE) D(2S)ψππWANG 15A (BELLE)

(2S)ψππLEES 14F (BABAR)

cΛcΛPAKHLOVA 08B (BELLE)

StatesψPDG 2020

3700 3800 3900 4000 4100 4200 4300 4400 4500 4600 4700

Mass [MeV]

0

20

40

60

80

100

120

140

160

Wid

th

[MeV

]

StatesψPDG 2020

R peaksABLIKIM 08D (BESII) R

µµ K→AAIJ 13BC (LHCb) B (4230)ψ

c0χωABLIKIM 19AI (BESIII)

DD*πABLIKIM 19R (BESIII) X(3872)γABLIKIM 19V (BESIII)

ψJ/ππABLIKIM 17B (BESIII)

chππABLIKIM 17G (BESIII) (2S)ψππABLIKIM 17V (BESIII)

(4360)ψ

ψJ/ππABLIKIM 17B (BESIII) (2S)ψππABLIKIM 17V (BESIII)

(2S)ψππWANG 15A (BELLE) (2S)ψππLEES 14F (BABAR)

(4390)ψ

chππABLIKIM 17G (BESIII) (4660)ψ

s1Ds

JIA 19A (BELLE) D(2S)ψππWANG 15A (BELLE)

(2S)ψππLEES 14F (BABAR)

cΛcΛPAKHLOVA 08B (BELLE)

StatesψPDG 2020


8








A few notes:






⟹⟹⟹


1 8. Naming Scheme for Hadrons

8. Naming Scheme for Hadrons

Revised August 2019 by V. Burkert (Je�erson Lab), S. Eidelman (Budker Inst., Novosibirsk; Novosi-birsk U.), C. Hanhart (Jülich), E. Klempt (Bonn U.), R.E. Mitchell (Indiana U.), U. Thoma (BonnU.), L. Tiator (KPH, JGU Mainz) and R.L. Workman (George Washington U.).

In the 1986 edition [1], the Particle Data Group extended and systematized the naming schemefor mesons and baryons. The extensions were necessary in order to name the new particles con-taining c or b quarks that were rapidly being discovered. With the discoveries of particles that arecandidates for states with more complicated structures than just qq or qqq, it is necessary to extendthe naming scheme again.

8.1 “Neutral-flavor” mesonsThe naming of mesons is based on their quantum numbers. Although we use names established

within the naive quark model, the name does not necessarily designate a (predominantly) qq state.In other words, the name provides information on the quantum numbers of a given state and notabout its dominant component, which might well be qq (if allowed) or tetraquark, molecule, etc.In many cases, exotic states will be di�cult to distinguish from qq states and will likely mix withthem, and we make no attempt to, e.g., distinguish those that are “mostly gluonium” from thosethat are “mostly qq.”

Table 8.1: Symbols for mesons with strangeness and heavy-flavor quan-tum numbers equal to zero. States that do not yet appear in the RPP arelisted in parentheses.

JP C =I 0≠+ 1+≠ 1≠≠ 0++

2≠+ 3+≠ 2≠≠ 1++

......

......

Minimal quark contentud, uu ≠ dd, du (I = 1) fi b fl add + uu and/or ss (I = 0) ÷,÷Õ h,hÕ Ê,„ f ,f Õ

cc ÷c hc Âú ‰c

bb ÷b hb Ã ‰b

I = 1 with cc ( c) Zc Rc (Wc)I = 1 with bb ( b) Zb (Rb) (Wb)

úThe J/Â remains the J/Â.

Table 8.1 shows the names for mesons having strangeness and all heavy-flavor quantum numbersequal to zero. The rows of Table 8.1 give the minimal qq content. The columns give the possibleparity/charge-conjugation states,

PC = ≠+, +≠, ≠≠, and ++ .Within the naive quark model, these combinations correspond one-to-one to the angular-momentumstate 2S+1LJ of the qq system being

1(L even)J , 1(L odd)J , 3(L even)J , or 3(L odd)J ,

respectively. Here S, L, and J are the spin, orbital, and total angular momenta of the qq system.Within the naive quark model, the quantum numbers are related by P = (≠1)L+1, C = (≠1)L+S ,

P.A. Zyla et al. (Particle Data Group), Prog. Theor. Exp. Phys. 2020, 083C01 (2020)14th September, 2020 2:38pm








JP C =I 0≠+ 1+≠ 1≠≠ 0++

2≠+ 3+≠ 2≠≠ 1++

......

......


cc ÷c hc Âú ‰c

bb ÷b hb Ã ‰b








meson names are based solely on quantum numbers (but original names are also kept)


χc1(3872) IG (JPC ) = 0+(1 + +)

also known as X (3872)This state shows properties different from a conventional qq state.A candidate for an exotic structure. See the review on non-qq states.

First observed by CHOI 03 in B → K π+π− J/ψ(1S) decays as a

narrow peak in the invariant mass distribution of the π+π− J/ψ(1S)final state. Isovector hypothesis excluded by AUBERT 05B andCHOI 11.

AAIJ 13Q perform a full five-dimensional amplitude analysis of

the angular correlations between the decay products in B+→

χc1(3872)K+ decays, where χc1(3872) → J/ψπ+π− and J/ψ →

µ+µ−, which unambiguously gives the JPC = 1 ++ assignment

under the assumption that the π+π− and J/ψ are in an S-wave.AAIJ 15AO extend this analysis with more data to limit D-wavecontributions to < 4% at 95% CL.

See the review on “Spectroscopy of Mesons Containing Two HeavyQuarks.”

χc1(3872) MASS FROM J/ψX MODEχc1(3872) MASS FROM J/ψX MODEχc1(3872) MASS FROM J/ψX MODEχc1(3872) MASS FROM J/ψX MODE


3871.65 ± 0.06 OUR AVERAGE3871.65 ± 0.06 OUR AVERAGE3871.65 ± 0.06 OUR AVERAGE3871.65 ± 0.06 OUR AVERAGE

3871.64 ± 0.06 ±0.01 19.8k 1 AAIJ 20S LHCB B+ →

J/ψπ+ π−K+

3871.9 ± 0.7 ±0.2 20 ABLIKIM 14 BES3 e+ e− →

J/ψπ+ π−γ3871.95 ± 0.48 ±0.12 0.6k AAIJ 12H LHCB pp → J/ψπ+π−X

3871.85 ± 0.27 ±0.19 170 2 CHOI 11 BELL B → K π+π− J/ψ

3873 + 1.8− 1.6 ±1.3 27 3 DEL-AMO-SA...10B BABR B → ωJ/ψK

3871.61 ± 0.16 ±0.19 6k 3,4 AALTONEN 09AU CDF2 pp → J/ψπ+π−X

3871.4 ± 0.6 ±0.1 93.4 AUBERT 08Y BABR B+ →

K+ J/ψπ+π−

3868.7 ± 1.5 ±0.4 9.4 AUBERT 08Y BABR B0 →

K0SJ/ψπ+π−

3871.8 ± 3.1 ±3.0 522 3,5 ABAZOV 04F D0 pp → J/ψπ+π−X


3871.695± 0.067±0.068 15.6k 6 AAIJ 20AD LHCB pp → J/ψπ+π−X

3871.59 ± 0.06 ±0.03 4.2k 7 AAIJ 20S LHCB B+ →

J/ψπ+ π−K+

3873.3 ± 1.1 ±1.0 45 8 ABLIKIM 19V BES e+ e− → γωJ/ψ

3860.0 ±10.4 13.6 3,9 AGHASYAN 18A COMP γ∗N → X π±N′

3868.6 ± 1.2 ±0.2 8 10 AUBERT 06 BABR B0 →

K0SJ/ψπ+π−



9








A few notes:






⟹⟹⟹









JP C =I 0≠+ 1+≠ 1≠≠ 0++

2≠+ 3+≠ 2≠≠ 1++

......

......


cc ÷c hc Âú ‰c

bb ÷b hb Ã ‰b















JP C =I 0≠+ 1+≠ 1≠≠ 0++

2≠+ 3+≠ 2≠≠ 1++

......

......


cc ÷c hc Âú ‰c

bb ÷b hb Ã ‰b









Observation of a Near-Threshold Structure in the K + Recoil-MassSpectra in e + e− → K + ðD−

s D"0 +D"−s D0 Þ

M. Ablikim,1 M. N. Achasov,10,c P. Adlarson,67 S. Ahmed,15 M. Albrecht,4 R. Aliberti,28 A. Amoroso,66a,66c Q. An,63,50

Anita,21 X. H. Bai,57 Y. Bai,49 O. Bakina,29 R. Baldini Ferroli,23a I. Balossino,24a Y. Ban,39,k K. Begzsuren,26 N. Berger,28

M. Bertani,23a D. Bettoni,24a F. Bianchi,66a,66c J. Biernat,67 J. Bloms,60 A. Bortone,66a,66c I. Boyko,29 R. A. Briere,5 H. Cai,68

X. Cai,1,50 A. Calcaterra,23a G. F. Cao,1,55 N. Cao,1,55 S. A. Cetin,54a J. F. Chang,1,50 W. L. Chang,1,55 G. Chelkov,29,b

D. Y. Chen,6 G. Chen,1 H. S. Chen,1,55 M. L. Chen,1,50 S. J. Chen,36 X. R. Chen,25 Y. B. Chen,1,50 Z. J. Chen,20,l

W. S. Cheng,66c G. Cibinetto,24a F. Cossio,66c X. F. Cui,37 H. L. Dai,1,50 X. C. Dai,1,55 A. Dbeyssi,15 R. B. de Boer,4

D. Dedovich,29 Z. Y. Deng,1 A. Denig,28 I. Denysenko,29 M. Destefanis,66a,66c F. De Mori,66a,66c Y. Ding,34 C. Dong,37

J. Dong,1,50 L. Y. Dong,1,55 M. Y. Dong,1,50,55 X. Dong,68 S. X. Du,71 J. Fang,1,50 S. S. Fang,1,55 Y. Fang,1 R. Farinelli,24a

L. Fava,66b,66c F. Feldbauer,4 G. Felici,23a C. Q. Feng,63,50 M. Fritsch,4 C. D. Fu,1 Y. Fu,1 Y. Gao,39,k Y. Gao,64 Y. Gao,63,50

Y. G. Gao,6 I. Garzia,24a,24b E. M. Gersabeck,58 A. Gilman,59 K. Goetzen,11 L. Gong,34 W. X. Gong,1,50 W. Gradl,28

M. Greco,66a,66c L. M. Gu,36 M. H. Gu,1,50 S. Gu,2 Y. T. Gu,13 C. Y. Guan,1,55 A. Q. Guo,22 L. B. Guo,35 R. P. Guo,41

Y. P. Guo,9,h Y. P. Guo,28 A. Guskov,29 T. T. Han,42 X. Q. Hao,16 F. A. Harris,56 K. L. He,1,55 F. H. Heinsius,4 C. H. Heinz,28

T. Held,4 Y. K. Heng,1,50,55 C. Herold,52 M. Himmelreich,11,f T. Holtmann,4 Y. R. Hou,55 Z. L. Hou,1 H. M. Hu,1,55 J. F. Hu,48,m T. Hu,1,50,55 Y. Hu,1 G. S. Huang,63,50 L. Q. Huang,64 X. T. Huang,42 Y. P. Huang,1 Z. Huang,39,k N. Huesken,60

T. Hussain,65 W. Ikegami Andersson,67 W. Imoehl,22 M. Irshad,63,50 S. Jaeger,4 S. Janchiv,26,j Q. Ji,1 Q. P. Ji,16 X. B. Ji,1,55

X. L. Ji,1,50 H. B. Jiang,42 X. S. Jiang,1,50,55 X. Y. Jiang,37 Y. Jiang,55 J. B. Jiao,42 Z. Jiao,18 S. Jin,36 Y. Jin,57 T. Johansson,67

N. Kalantar-Nayestanaki,31 X. S. Kang,34 R. Kappert,31 M. Kavatsyuk,31 B. C. Ke,44,1 I. K. Keshk,4 A. Khoukaz,60

P. Kiese,28 R. Kiuchi,1 R. Kliemt,11 L. Koch,30 O. B. Kolcu,54a,e B. Kopf,4 M. Kuemmel,4 M. Kuessner,4 A. Kupsc,67

M. G. Kurth,1,55 W. Kühn,30 J. J. Lane,58 J. S. Lange,30 P. Larin,15 L. Lavezzi,66a,66c Z. H. Lei,63,50 H. Leithoff,28

M. Lellmann,28 T. Lenz,28 C. Li,40 C. H. Li,33 Cheng Li,63,50 D. M. Li,71 F. Li,1,50 G. Li,1 H. Li,44 H. Li,63,50 H. B. Li,1,55

H. J. Li,9,h J. L. Li,42 J. Q. Li,4 Ke Li,1 L. K. Li,1 Lei Li,3 P. L. Li,63,50 P. R. Li,32,n,o S. Y. Li,53 W. D. Li,1,55 W. G. Li,1

X. H. Li,63,50 X. L. Li,42 Z. Y. Li,51 H. Liang,63,50 H. Liang,1,55 Y. F. Liang,46 Y. T. Liang,25 L. Z. Liao,1,55 J. Libby,21

C. X. Lin,51 B. J. Liu,1 C. X. Liu,1 D. Liu,63,50 F. H. Liu,45 Fang Liu,1 Feng Liu,6 H. B. Liu,13 H. M. Liu,1,55 Huanhuan Liu,1

Huihui Liu,17 J. B. Liu,63,50 J. Y. Liu,1,55 K. Liu,1 K. Y. Liu,34 Ke Liu,6 L. Liu,63,50 M. H. Liu,9,h Q. Liu,55 S. B. Liu,63,50

Shuai Liu,47 T. Liu,1,55 W.M. Liu,63,50 X. Liu,32 Y. Liu,32 Y. B. Liu,37 Z. A. Liu,1,50,55 Z. Q. Liu,42 X. C. Lou,1,50,55 F. X. Lu,16

H. J. Lu,18 J. D. Lu,1,55 J. G. Lu,1,50 X. L. Lu,1 Y. Lu,1 Y. P. Lu,1,50 C. L. Luo,35 M. X. Luo,70 P.W. Luo,51 T. Luo,9,h

X. L. Luo,1,50 S. Lusso,66c X. R. Lyu,55 F. C. Ma,34 H. L. Ma,1 L. L. Ma,42 M. M. Ma,1,55 Q. M. Ma,1 R. Q. Ma,1,55

R. T. Ma,55 X. N. Ma,37 X. X. Ma,1,55 X. Y. Ma,1,50 F. E. Maas,15 M. Maggiora,66a,66c S. Maldaner,28 S. Malde,61

Q. A. Malik,65 A. Mangoni,23b Y. J. Mao,39,k Z. P. Mao,1 S. Marcello,66a,66c Z. X. Meng,57 J. G. Messchendorp,31

G. Mezzadri,24a T. J. Min,36 R. E. Mitchell,22 X. H. Mo,1,50,55 Y. J. Mo,6 N. Yu. Muchnoi,10,c H. Muramatsu,59 S. Nakhoul,11,f

Y. Nefedov,29 F. Nerling,11,f I. B. Nikolaev,10,c Z. Ning,1,50 S. Nisar,8,i S. L. Olsen,55 Q. Ouyang,1,50,55 S. Pacetti,23b,23c

X. Pan,9,h Y. Pan,58 A. Pathak,1 P. Patteri,23a M. Pelizaeus,4 H. P. Peng,63,50 K. Peters,11,f J. Pettersson,67 J. L. Ping,35

R. G. Ping,1,55 A. Pitka,4 R. Poling,59 V. Prasad,63,50 H. Qi,63,50 H. R. Qi,53 K. H. Qi,25 M. Qi,36 T. Y. Qi,9 T. Y. Qi,2

S. Qian,1,50 W. B. Qian,55 Z. Qian,51 C. F. Qiao,55 L. Q. Qin,12 X. S. Qin,42 Z. H. Qin,1,50 J. F. Qiu,1 S. Q. Qu,37

K. H. Rashid,65 K. Ravindran,21 C. F. Redmer,28 A. Rivetti,66c V. Rodin,31 M. Rolo,66c G. Rong,1,55 Ch. Rosner,15

M. Rump,60 H. S. Sang,63 A. Sarantsev,29,d Y. Schelhaas,28 C. Schnier,4 K. Schoenning,67 M. Scodeggio,24a D. C. Shan,47

W. Shan,19 X. Y. Shan,63,50 M. Shao,63,50 C. P. Shen,9 P. X. Shen,37 X. Y. Shen,1,55 B. A. Shi,55 H. C. Shi,63,50 R. S. Shi,1,55

X. Shi,1,50 X. D. Shi,63,50 W.M. Song,27,1 Y. X. Song,39,k S. Sosio,66a,66c S. Spataro,66a,66c K. X. Su,68 F. F. Sui,42 G. X. Sun,1

H. K. Sun,1 J. F. Sun,16 L. Sun,68 S. S. Sun,1,55 T. Sun,1,55 W. Y. Sun,35 X. Sun,20,l Y. J. Sun,63,50 Y. K. Sun,63,50 Y. Z. Sun,1

Z. T. Sun,1 Y. H. Tan,68 Y. X. Tan,63,50 C. J. Tang,46 G. Y. Tang,1 J. Tang,51 J. X. Teng,63,50 V. Thoren,67 I. Uman,54b

C.W. Wang,36 D. Y. Wang,39,k H. J. Wang,55 H. P. Wang,1,55 K. Wang,1,50 L. L. Wang,1 M. Wang,42 M. Z. Wang,39,k

Meng Wang,1,55 W. H. Wang,68 W. P. Wang,63,50 X. Wang,39,k X. F. Wang,32 X. L. Wang,9,h Y. Wang,51 Y. Wang,63,50

Y. D. Wang,38 Y. F. Wang,1,50,55 Y. Q. Wang,1 Z. Wang,1,50 Z. Y. Wang,1 Ziyi Wang,55 Zongyuan Wang,1,55 D. H. Wei,12

P. Weidenkaff,28 F. Weidner,60 S. P. Wen,1 D. J. White,58 U. Wiedner,4 G. Wilkinson,61 M. Wolke,67 L. Wollenberg,4

J. F. Wu,1,55 L. H. Wu,1 L. J. Wu,1,55 X. Wu,9,h Z. Wu,1,50 L. Xia,63,50 H. Xiao,9,h S. Y. Xiao,1 Y. J. Xiao,1,55 Z. J. Xiao,35

X. H. Xie,39,k Y. G. Xie,1,50 Y. H. Xie,6 T. Y. Xing,1,55 G. F. Xu,1 J. J. Xu,36 Q. J. Xu,14 W. Xu,1,55 X. P. Xu,47 Y. C. Xu,55

PHYSICAL REVIEW LETTERS 126, 102001 (2021)Editors' Suggestion Featured in Physics

0031-9007=21=126(10)=102001(8) 102001-1 Published by the American Physical Society

resolution compared to RMðKþD−s Þ [10]. A clear peak is

seen in this distribution at the nominal D$0 mass, whichcorresponds to the final state KþD−

s D$0. There is also acontribution from KþD$−

s D0, which appears as a broaderstructure beneath the KþD−

s D$0 signal. Therefore, werequire RMðKþD−

s Þ þMðD−s Þ −mðD−

s Þ to be in theinterval ð1.990; 2.027Þ GeV=c2 to isolate the signalcandidates of both signal processes.To estimate the shape of combinatorial background, we

use wrong-sign (WS) combinations of D−s and K− candi-

dates, rather than the right-sign D−s and Kþ candidates. The

WS K−D−s recoil-mass distribution, scaled by a factor of

1.18, agrees with the data distribution in the sidebandregions, ð1.91; 1.95Þ GeV=c2 and ð2.08; 2.11Þ GeV=c2, asshown in Fig. 2. The number of background events withinthe signal region is estimated to be 282.6% 12.0 by a fit tothe sideband data with a linear function, whose slope isdetermined from the WS data. In addition, the WS eventsare used to represent the combinatorial-background distri-bution of the recoil mass of the bachelor Kþ. This techniquehas been used previously in the observation of theZcð4025Þþ at BESIII [10]. We validate the use of the WSdata-driven background modeling of both the RMðKþD−

s Þand RMðKþÞ spectra by comparing the correspondingdistributions between WS combinations and background-only contributions. Furthermore, the RMðKþÞ distributionof the events in the sideband regions in Fig. 2 agrees wellwith that of the corresponding WS data.Figure 3(a) shows the RMðKþÞ distribution for events atffiffiffis

p¼ 4.681 GeV; an enhancement is evident in the region

RMðKþÞ < 4 GeV=c2 compared to the expectation from theWS events. This is clearly illustrated in the RMðKþÞ distri-bution in data with subtraction of the WS component inFig. 4. The enhancement cannot be attributed to the NRsignal processes eþe− → KþðD−

s D$0 þD$−s D0Þ. To under-

stand potential contributions from the processes eþe− →Dð$Þ−

s D$$þs ð→ Dð$Þ0KþÞ or Dð$Þ0D$$0ð→ Dð$Þ−

s KþÞ, weexamine all known D$$

ðsÞ excited states [29,32] using MCsimulation samples. Dedicated exclusive MC studies showthat none of these processes, including possible interferenceeffects, exhibit a narrow structure below 4.0 GeV=c2 [28].The following three processes that contain excited

D$$þs background have potential contributions to the

RMðKþÞ spectrum: (1) D−s D$

s1ð2536Þþð→ D$0KþÞ,(2) D$−

s D$s2ð2573Þþð→ D0KþÞ, and (3) D−

s D$s1ð2700Þþ

ð→ D$0KþÞ. We estimate their production cross sectionsby studying several control samples. The yields for channel(1) are estimated by analyzing the D$

s1ð2536Þþ peak in theD$0Kþ mass spectra using two separate partially recon-structed samples: KþD−

s (with D$0 missing) and KþD$0

(with D−s missing). For channel (2), control samples are

selected by reconstructing D0Kþγ (with missing D−s ) or

KþD$−s (with missing D0). The D$

s2ð2573Þþ yield isobtained from combined fits to the D0Kþ mass spectra.From this, the contribution from channel (2) to the signal

candidates in Fig. 3 is evaluated. For channel (3), a controlsample of eþe− → D−

s D$s1ð2700Þþð→ D0KþÞ is selected

by detecting the D−s Kþ recoiling against a missing D0.

We then use the BF ratio of B(D$s1ð2700Þþ → D$0Kþ)=

B(D$s1ð2700Þþ → D0Kþ) ¼ 0.91% 0.18 [33] to estimate

the strength of this background contribution. The shapes inRMðKþÞ of these three channels are extracted from MCsamples, whereas the normalization is derived from thecontrol samples. The estimated background contributionsof the channels (1), (2), and (3) in the RMðKþÞ spectrum atffiffiffis

p¼ 4.681 GeV are 54.4% 8.0, 19.1% 7.6, and 15.0%

13.3 events, respectively. For the other energy points, theestimated yields of the three channels are given in Ref. [28].

)2) (GeV/c+RM(K

)2Ev

ents

/(5.0

MeV

/c

4 4.10

5

10

15

20 = 4.661 GeVs

(d)

4 4.05 4.1 4.15

= 4.698 GeVs(e)

4 4.05 4.10

5

10

15

20 = 4.628 GeVs

(b)

4 4.05 4.1

= 4.641 GeVs(c)

4 4.05 4.1 4.150

10

20

30

40 = 4.681 GeVs

(a)

Data

Total fit-(3985)csZ

0D*D 0(2600)1

*

non-Res.(*)s Ds

**D

comb. BKG

FIG. 3. Simultaneous unbinned maximum likelihood fit tothe Kþ recoil-mass spectra in data at

ffiffiffis

p¼ 4.628, 4.641,

4.661, 4.681, and 4.698 GeV. Note that the size of theD$0D$

1ð2600Þ0ð→ D−s KþÞ component is consistent with zero.

)2) (GeV/c+RM(K4 4.05 4.1 4.15

2Ev

ents/

5.0 M

eV/c

-10

0

10

20

30

40Data

(*)sD

**sD

non-Res.

= 4.681 GeVs

FIG. 4. The Kþ recoil-mass spectrum in data atffiffiffis

p¼

4.681 GeV after subtraction of the combinatorial backgrounds.

PHYSICAL REVIEW LETTERS 126, 102001 (2021)

102001-5






















s1ð2536Þþð→ D$0KþÞ,(2) D$−


s D$s1ð2700Þþ














p¼ 4.681 GeV are 54.4% 8.0, 19.1% 7.6, and 15.0%


)2) (GeV/c+RM(K

)2Ev

ents

/(5.0

MeV

/c

4 4.10

5

10

15

20 = 4.661 GeVs

(d)

4 4.05 4.1 4.15

= 4.698 GeVs(e)

4 4.05 4.10

5

10

15

20 = 4.628 GeVs

(b)

4 4.05 4.1

= 4.641 GeVs(c)

4 4.05 4.1 4.150

10

20

30

40 = 4.681 GeVs

(a)

Data

Total fit-(3985)csZ

0D*D 0(2600)1

*

non-Res.(*)s Ds

**D

comb. BKG


ffiffiffis

p¼ 4.628, 4.641,



)2) (GeV/c+RM(K4 4.05 4.1 4.15

2Ev

ents/

5.0 M

eV/c

-10

0

10

20

30

40Data

(*)sD

**sD

non-Res.

= 4.681 GeVs


p¼



102001-5






















s1ð2536Þþð→ D$0KþÞ,(2) D$−


s D$s1ð2700Þþ














p¼ 4.681 GeV are 54.4% 8.0, 19.1% 7.6, and 15.0%


)2) (GeV/c+RM(K

)2Ev

ents

/(5.0

MeV

/c

4 4.10

5

10

15

20 = 4.661 GeVs

(d)

4 4.05 4.1 4.15

= 4.698 GeVs(e)

4 4.05 4.10

5

10

15

20 = 4.628 GeVs

(b)

4 4.05 4.1

= 4.641 GeVs(c)

4 4.05 4.1 4.150

10

20

30

40 = 4.681 GeVs

(a)

Data

Total fit-(3985)csZ

0D*D 0(2600)1

*

non-Res.(*)s Ds

**D

comb. BKG


ffiffiffis

p¼ 4.628, 4.641,



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F. Yan,9 ,h L. Yan,66a,66c L. Yan,9 ,h W. B. Yan,63,50 W. C. Yan,71 Xu Yan,47 H. J. Yang,43,g H. X. Yang,1 L. Yang,44

R. X. Yang,63,50 S. L. Yang,55 S. L. Yang,1,55 Y. H. Yang,36 Y. X. Yang,12 Yifan Yang,1,55 Zhi Yang,25 M. Ye,1,50 M. H. Ye,7

J. H. Yin,1 Z. Y. You,51 B. X. Yu,1,50,55 C. X. Yu,37 G. Yu,1,55 J. S. Yu,20,l T. Yu,64 C. Z. Yuan,1,55 L. Yuan,2 W. Yuan,66a,66c

X. Q. Yuan,39 ,k Y. Yuan,1 Z. Y. Yuan,51 C. X. Yue,33 A. Yuncu,54b,a A. A. Zafar,65 Y. Zeng,20,l B. X. Zhang,1

Guangyi Zhang,16 H. Zhang,63 H. H. Zhang,51 H. Y. Zhang,1,50 J. J. Zhang,44 J. L. Zhang,69 J. Q. Zhang,4 J. W. Zhang,1,50,55

J. Y. Zhang,1 J. Z. Zhang,1,55 Jianyu Zhang,1,55 Jiawei Zhang,1,55 Lei Zhang,36 S. Zhang,51 S. F. Zhang,36 Shulei Zhang,20,l

X. D. Zhang,38 X. Y. Zhang,42 Y. Zhang,61 Y. H. Zhang,1,50 Y. T. Zhang,63,50 Yan Zhang,63,50 Yao Zhang,1 Yi Zhang,9 ,h Z.H. Zhang,6 Z. Y. Zhang,68 G. Zhao,1 J. Zhao,33 J. Y. Zhao,1,55 J. Z. Zhao,1,50 Lei Zhao,63,50 Ling Zhao,1 M. G. Zhao,37

Q. Zhao,1 S. J. Zhao,71 Y. B. Zhao,1,50 Y. X. Zhao,25 Z. G. Zhao,63,50 A. Zhemchugov,29 ,b B. Zheng,64 J. P. Zheng,1,50

Y. Zheng,39 ,k Y. H. Zheng,55 B. Zhong,35 C. Zhong,64 L. P. Zhou,1,55 Q. Zhou,1,55 X. Zhou,68 X. K. Zhou,55 X. R. Zhou,63,50

A. N. Zhu,1,55 J. Zhu,37 K. Zhu,1 K. J. Zhu,1,50,55 S. H. Zhu,62 T. J. Zhu,69 W. J. Zhu,37 X. L. Zhu,53 Y. C. Zhu,63,50

Z. A. Zhu,1,55 B. S. Zou,1 and J. H. Zou1

(BESIII Collaboration)

1Institute of High Energy Physics, Beijing 100049, People’s Republic of China2Beihang University, Beijing 100191, People’s Republic of China

3Beijing Institute of Petrochemical Technology, Beijing 102617, People’s Republic of China4Bochum Ruhr-University, D-44780 Bochum, Germany

5Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA6Central China Normal University, Wuhan 430079, People’s Republic of China

7China Center of Advanced Science and Technology, Beijing 100190, People’s Republic of China8COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, 54000 Lahore, Pakistan

9Fudan University, Shanghai 200443, People’s Republic of China10G.I. Budker Institute of Nuclear Physics SB RAS (BINP), Novosibirsk 630090, Russia11GSI Helmholtzcentre for Heavy Ion Research GmbH, D-64291 Darmstadt, Germany

12Guangxi Normal University, Guilin 541004, People’s Republic of China13Guangxi University, Nanning 530004, People’s Republic of China

14Hangzhou Normal University, Hangzhou 310036, People’s Republic of China15Helmholtz Institute Mainz, Johann-Joachim-Becher-Weg 45, D-55099 Mainz, Germany

16Henan Normal University, Xinxiang 453007, People’s Republic of China17Henan University of Science and Technology, Luoyang 471003, People’s Republic of China

18Huangshan College, Huangshan 245000, People’s Republic of China19Hunan Normal University, Changsha 410081, People’s Republic of China

20Hunan University, Changsha 410082, People’s Republic of China21Indian Institute of Technology Madras, Chennai 600036, India

22Indiana University, Bloomington, Indiana 47405, USA23aINFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy

23bINFN Sezione di Perugia, I-06100 Perugia, Italy23cUniversity of Perugia, I-06100 Perugia, Italy

24aINFN Sezione di Ferrara, I-44122, Ferrara, Italy24bUniversity of Ferrara, I-44122, Ferrara, Italy

25Institute of Modern Physics, Lanzhou 730000, People’s Republic of China26Institute of Physics and Technology, Peace Avenue 54B, Ulaanbaatar 13330, Mongolia

27Jilin University, Changchun 130012, People’s Republic of China28Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, D-55099 Mainz, Germany

29Joint Institute for Nuclear Research, 141980 Dubna, Moscow region, Russia30Justus-Liebig-Universitaet Giessen, II. Physikalisches Institut, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany

31KVI-CART, University of Groningen, NL-9747 AA Groningen, The Netherlands32Lanzhou University, Lanzhou 730000, People’s Republic of China

33Liaoning Normal University, Dalian 116029, People’s Republic of China34Liaoning University, Shenyang 110036, People’s Republic of China

35Nanjing Normal University, Nanjing 210023, People’s Republic of China36Nanjing University, Nanjing 210093, People’s Republic of China37Nankai University, Tianjin 300071, People’s Republic of China

38North China Electric Power University, Beijing 102206, People’s Republic of China39Peking University, Beijing 100871, People’s Republic of China

40Qufu Normal University, Qufu 273165, People’s Republic of China


102001-2

Zcs(3985)

easy extension from , , etc. to , , etc.Zc Zb Zcs Zbs


10








A few notes:






⟹⟹⟹









JP C =I 0≠+ 1+≠ 1≠≠ 0++

2≠+ 3+≠ 2≠≠ 1++

......

......


cc ÷c hc Âú ‰c

bb ÷b hb Ã ‰b















JP C =I 0≠+ 1+≠ 1≠≠ 0++

2≠+ 3+≠ 2≠≠ 1++

......

......


cc ÷c hc Âú ‰c

bb ÷b hb Ã ‰b









Article

Observation of structure in the J/w -pair mass spectrum

LHCb collaboration 1

a r t i c l e i n f o

Article history:Received 1 July 2020Received in revised form 28 July 2020Accepted 19 August 2020Available online 29 August 2020

Keywords:QCDExoticsTetraquarkSpectroscopyQuarkoniumParticle and resonance production

a b s t r a c t

Using proton-proton collision data at centre-of-mass energies offfiffis

p¼ 7;8 and 13 TeV recorded by the

LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9 fb"1, theinvariant mass spectrum of J/w pairs is studied. A narrow structure around 6:9 GeV=c2 matching the line-shape of a resonance and a broad structure just above twice the J/w mass are observed. The deviation ofthe data from nonresonant J/w -pair production is above five standard deviations in the mass regionbetween 6:2 and 7:4 GeV=c2, covering predicted masses of states composed of four charm quarks. Themass and natural width of the narrow X 6900ð Þ structure are measured assuming a Breit-Wignerlineshape.! 2020 Science China Press. Published by Elsevier B.V. and Science China Press. This is an open access

article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

1. Introduction

The strong interaction is one of the fundamental forces of nat-ure and it governs the dynamics of quarks and gluons. Accordingto quantum chromodynamics (QCD), the theory describing thestrong interaction, quarks are confined into hadrons, in agreementwith experimental observations. The quark model [1,2] classifieshadrons into conventional mesons (qq) and baryons (qqq or qqq),and also allows for the existence of exotic hadrons such as tetra-quarks (qqqq) and pentaquarks (qqqqq). Exotic states provide aunique environment to study the strong interaction and the con-finement mechanism [3]. The first experimental evidence for anexotic hadron candidate was the vc1 3872ð Þ state observed in2003 by the Belle collaboration [4]. Since then a series of novelstates consistent with containing four quarks have been discovered[5]. Recently, the LHCb collaboration observed resonances inter-preted to be pentaquark states [6–9]. All hadrons observed to date,including those of exotic nature, contain at most two heavy charm(c) or bottom (b) quarks, whereas many QCD-motivated phe-nomenological models also predict the existence of states consist-ing of four heavy quarks, i.e. TQ1Q2Q3Q4

, where Qi is a c or a b quark[10–35]. Theoretically, the interpretation of the internal structureof such states usually assumes the formation of a Q1Q2 diquarkand a Q3Q4 antidiquark attracting each other. Application of thisdiquark model successfully predicts the mass of the doubly

charmed baryon Nþþcc [36,37] and helps to explain the relative rates

of bottom baryon decays [38].Tetraquark states comprising only bottom quarks, Tbbbb, have

been searched for by the LHCb and CMS collaborations in the!lþl" decay [39,40], with the ! state consisting of a bb pair. How-ever, the four-charm states, have not yet been studied in detailexperimentally. A state could disintegrate into a pair of charmo-nium states such as J/w mesons, with each consisting of a cc pair.Decays to a J/w meson plus a heavier charmonium state, or twoheavier charmonium states, with the heavier states decaying sub-sequently into a J/w meson and accompanying particles, are alsopossible. Predictions for the masses of states vary from 5:8 to7:4 GeV=c2 [10–26], which are above the masses of known charmo-nia and charmonium-like exotic states and below those of bot-tomonium hadrons. 2 This mass range guarantees a cleanexperimental environment to identify possible states in the J/w -pair (also referred to as di-J/w ) invariant mass (Mdi-J=w ) spectrum.

In proton-proton (pp) collisions, a pair of J/w mesons can be pro-duced in two separate interactions of gluons or quarks, nameddouble-parton scattering (DPS) [41–43], or in a single interaction,named single-parton scattering (SPS) [44–51]. The SPS processincludes both resonant production via intermediate states, whichcould be tetraquarks, and nonresonant production. Within theDPS process, the two J/w mesons are usually assumed to be pro-duced independently, thus the distribution of any di-J/w observ-

https://doi.org/10.1016/j.scib.2020.08.0322095-9273/! 2020 Science China Press. Published by Elsevier B.V. and Science China Press.This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

1 Authors are listed at the end of this paper.

2 Energy units MeV ¼ 106 eV, GeV ¼ 109 eV and TeV ¼ 1012 eV are used in thispaper.

Science Bulletin 65 (2020) 1983–1993

Contents lists available at ScienceDirect

Science Bulletin

journal homepage: www.elsevier .com/locate /sc ib

nificance. Considering the sample in the p di-J=wT > 5:2 GeV=c region,

the null hypothesis is inconsistent with the data at 3:4 standarddeviations (r). A test performed simultaneously in the aforemen-tioned six p di-J=w

T regions yields a discrepancy of 6:0r with the nullhypothesis. A higher value is obtained in the latter case attributedto the presence of the structure at the same Mdi-J=w location in dif-

ferent p di-J=wT intervals. A cross-check is performed by dividing the

data into five or seven p di-J=wT regions instead, which results in sig-

nificance values consistent with the nominal 6:0r. The significancevalues are summarised in Table 1 (any structure beyond NRSPSplus DPS).

The structures in the Mdi-J=w distribution can have various inter-pretations. There may be one or more resonant states decayingdirectly into a pair of J/w mesons, or states decaying into a pairof J/w mesons through feed-down of heavier quarkonia, for exam-ple Tcc c

!c! ! vc ! J=w cð ÞJ=w where the photon escapes detection. In

the latter case, such a state would be expected to peak at a lowerMdi-J=w position, close to the di-J/w mass threshold, and its structurewould be broader compared to that from a direct decay. This feed-down is unlikely an explanation for the narrow X 6900ð Þ structure.Rescattering of two charmonium states produced by SPS close totheir mass threshold may also generate a narrow structure [88–91]. The two thresholds close to the X 6900ð Þ structure could beformed by vc0vc0 pairs at 6829:4 MeV=c2 and vc1vc0 pairs at6925:4 MeV=c2, respectively. Whereas a resonance is oftendescribed by a relativistic Breit-Wigner (BW) function [85], thelineshape of a structure with rescattering effects taken intoaccount is more complex. In principle, resonant production caninterfere with NRSPS of the same spin-parity quantum numbers(JPC), resulting in a coherent sum of the two components and thusa modification of the total Mdi-J=w distribution.

Two different models of the structure lineshape providing areasonable description of the data are investigated. The X 6900ð Þ

lineshape parameters and yields are derived from fits to thep di-J=wT -threshold sample. Simultaneous p di-J=w

T -binned fits are alsoperformed as a cross-check and the variation of lineshape param-eters is considered as a source of systematic uncertainties. Due toits low significance, the structure around 7:2 GeV=c2 has beenneglected.

In model I, the X 6900ð Þ structure is considered as a resonance,whereas the threshold enhancement is described through a super-position of two resonances. The lineshapes of these resonances aredescribed by S-wave relativistic BW functions multiplied by a two-body phase-space distribution. The experimental resolution onMdi-J=w is below 5 MeV=c2 over the full mass range and negligiblecompared to the widths of the structures. The projections of thep di-J=wT -threshold fit using this model are shown in Fig. 3b. The mass,

natural width and yield are determined to bem X 6900ð Þ½ % ¼ 6905 ' 11 MeV=c2, C X 6900ð Þ½ % ¼ 80 ' 19 MeV andNsig ¼ 252 ' 63, where biases on the statistical uncertainties havebeen corrected using a bootstrap method [92]. The goodness offit is studied using a v2 test statistic and found to bev2=ndof ¼ 112:7=89, corresponding to a probability of 4:6%. Thefit is also performed assuming the threshold enhancement as dueto a single wide resonance (see the Supplementary materials);the fit quality is found significantly poorer and thus this model isnot further investigated.

A comparison between the best fit result of model I and the datareveals a tension around 6:75 GeV=c2, where the data shows a dip.In an attempt to describe the dip, model II allows for interferencebetween the NRSPS component and a resonance for the thresholdenhancement. The coherent sum of the two components is definedas

Aei/ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffif nr Mdi-J=w

" #qþ BW Mdi-J=w

" #$$$$

$$$$2

; ð1Þ

Fig. 3. Invariant mass spectra of weighted di-J/w candidates with p di-J=wT > 5:2 GeV=c and overlaid projections of the p di-J=w

T -threshold fit using (a) the NRSPS plus DPS model,(b) model I, and (c) model II.

1986 LHCb collaboration / Science Bulletin 65 (2020) 1983–1993

harder extension to (ongoing) and (!!) [and also (??)]

Tcccc T +cc

X0/1(2900) → D−K+


11








A few notes:






⟹⟹⟹


June 14, 2021

PDG Reviews Responsibilities

PDG review responsibilities as of June 14, 2021. Please refer to the Responsibility or Reviews tools in PdgWorkspacefor the current assignment of review responsibilities.

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Agashe Bonventre Dynamical Electroweak Symmetry Breaking: Implications of theH0

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7

June 14, 2021








S. Spanier














1

June 14, 2021








S. Spanier














1

June 14, 2021








S. Spanier














1

Select upcoming reviews for meson spectroscopy

(new)

(new)


12








A few notes:






⟹⟹⟹



Baryons: Status and AimsEberhard Klempt University of Bonn

19th International Conference on Hadron Spectroscopy and StructureMexico City (Mexico), July 26 to 31, 2021.

Status: Baryon@PDG

2010 edition 2012 edition 2014 edition 2016 edition 2018 edition 2020 edition

Charles Charles Mike Mike Eberhard EberhardWohl Wohl Pennington Pennington Klempt Klempt

Ron Eberhard Volker Volker Volker VolkerWorkman Klempt Burkert Burkert Burkert Burkert

Ron Eberhard Eberhard Lothar LotharWorkman Klempt Klempt Tiator Tiator

Lothar Lothar Ron UlrikeTiator Tiator Workman Thoma

Ron2021: E. Klempt �! Volker Crede Workman

N(1440)P11 Why ⇤c(2880) PoleTables: ! not ⇤c(2880)5/2+? position

N(1440)1/2+ first

Minireview Note on Two-pole Resonances MinireviewReviews: on N and � electro- structure of E.K. + D.Asner on ⇤ and ⌃

revised production ⇤(1405) C. Hanhart revised

Decay modes of nucleon resonances ⇤⇤⇤⇤ Existence is certain.The impact of photoproduction black: PDG 2004 ⇤⇤⇤ Existence is very likely.

on baryon resonances red: PDG 2018 ⇤⇤ Evidence of existence is fair.blue: BESIII resonances ⇤ Evidence of existence is poor.

overall N� N⇡ �⇡ N� N⌘ ⇤K ⌃K N⇢ N! N⌘0 N1440⇡ N1520⇡ N1535⇡ N1680⇡

N 1/2+ ⇤⇤⇤⇤N(1440) 1/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤N(1520) 3/2� ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤ ⇤⇤⇤⇤N(1535) 1/2� ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤ ⇤ ⇤⇤⇤⇤N(1650) 1/2� ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤ ⇤ ⇤⇤⇤⇤ ⇤ ⇤N(1675) 5/2� ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤ ⇤⇤⇤ ⇤ ⇤ ⇤ ⇤N(1680) 5/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤ ⇤N(1700) 3/2� ⇤⇤⇤ ⇤⇤ ⇤⇤⇤ ⇤⇤⇤ ⇤ ⇤ ⇤N(1710) 1/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤ ⇤⇤⇤ ⇤⇤ ⇤ ⇤ ⇤ ⇤N(1720) 3/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤ ⇤ ⇤ ⇤⇤⇤⇤ ⇤ ⇤ ⇤N(1860) 5/2+ ⇤⇤ ⇤ ⇤⇤ ⇤ ⇤N(1875) 3/2� ⇤⇤⇤ ⇤⇤ ⇤⇤ ⇤ ⇤⇤ ⇤ ⇤ ⇤ ⇤ ⇤ ⇤ ⇤N(1880) 1/2+ ⇤⇤⇤ ⇤⇤ ⇤ ⇤⇤ ⇤ ⇤ ⇤⇤ ⇤⇤ ⇤⇤ ⇤N(1895) 1/2� ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤ ⇤ ⇤ ⇤⇤⇤⇤ ⇤⇤ ⇤⇤ ⇤ ⇤ ⇤⇤⇤⇤ ⇤N(1900) 3/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤ ⇤⇤ ⇤ ⇤ ⇤⇤ ⇤⇤ ⇤ ⇤⇤N(1990) 7/2+ ⇤⇤ ⇤⇤ ⇤⇤ ⇤ ⇤ ⇤ ⇤⇤ ⇤⇤N(2000) 5/2+ ⇤⇤ ⇤⇤ ⇤ ⇤⇤ ⇤ ⇤ ⇤N(2040) 3/2+ ⇤ ⇤N(2060) 5/2� ⇤⇤⇤ ⇤⇤⇤ ⇤⇤ ⇤ ⇤ ⇤ ⇤ ⇤ ⇤ ⇤ ⇤ ⇤ ⇤N(2100) 1/2+ ⇤⇤⇤ ⇤⇤ ⇤⇤⇤ ⇤⇤ ⇤⇤ ⇤ ⇤ ⇤ ⇤ ⇤⇤ ⇤⇤⇤N(2120) 3/2� ⇤⇤⇤ ⇤⇤⇤ ⇤⇤⇤ ⇤⇤ ⇤⇤ ⇤⇤ ⇤ ⇤ ⇤ ⇤ ⇤ ⇤N(2190) 7/2� ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤ ⇤ ⇤⇤ ⇤ ⇤ ⇤N(2220) 9/2+ ⇤⇤⇤⇤ ⇤⇤ ⇤⇤⇤⇤ ⇤ ⇤ ⇤N(2250) 9/2� ⇤⇤⇤⇤ ⇤⇤ ⇤⇤⇤⇤ ⇤ ⇤ ⇤N(2300) 1/2+ ⇤ ⇤N(2570) 5/2� ⇤ ⇤N(2600) 11/2� ⇤⇤⇤ ⇤⇤⇤N(2700) 13/2+ ⇤⇤ ⇤⇤ E. Klempt, 2019

Decay modes of � resonances ⇤⇤⇤⇤ Existence is certain.The impact of photoproduction black: PDG 2004 ⇤⇤⇤ Existence is very likely.on � resonances red: PDG 2018 ⇤⇤ Evidence of existence is fair.

⇤ Evidence of existence is poor.

overall N� N⇡ �⇡ ⌃K N⇢ �⌘ N1440⇡ N1520⇡ N1535⇡ N1680⇡

�(1232) 3/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤�(1600) 3/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤ ⇤⇤⇤⇤�(1620) 1/2� ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤�(1700) 3/2� ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤ ⇤ ⇤�(1750) 1/2+ ⇤ ⇤ ⇤ ⇤�(1900) 1/2� ⇤⇤⇤ ⇤⇤⇤ ⇤⇤⇤ ⇤ ⇤⇤ ⇤ ⇤ ⇤�(1905) 5/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤ ⇤ ⇤ ⇤⇤ ⇤�(1910) 1/2+ ⇤⇤⇤⇤ ⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤ ⇤⇤ ⇤ ⇤ ⇤�(1920) 3/2+ ⇤⇤⇤ ⇤⇤⇤ ⇤⇤⇤ ⇤⇤⇤ ⇤⇤ ⇤⇤�(1930) 5/2� ⇤⇤⇤ ⇤ ⇤⇤⇤ ⇤ ⇤�(1940) 3/2� ⇤⇤ ⇤ ⇤⇤ ⇤ ⇤ ⇤ ⇤ ⇤�(1950) 7/2+ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤⇤⇤ ⇤⇤ ⇤⇤⇤ ⇤�(2000) 5/2+ ⇤⇤ ⇤ ⇤⇤ ⇤ ⇤�(2150) 1/2� ⇤ ⇤�(2200) 7/2� ⇤⇤⇤ ⇤⇤⇤ ⇤⇤ ⇤⇤⇤ ⇤⇤�(2300) 9/2+ ⇤⇤ ⇤⇤�(2350) 5/2� ⇤ ⇤�(2390) 7/2+ ⇤ ⇤�(2400) 9/2� ⇤⇤ ⇤⇤ ⇤⇤�(2420) 11/2+ ⇤⇤⇤⇤ ⇤ ⇤⇤⇤⇤�(2750) 13/2� ⇤⇤ ⇤⇤�(2950) 15/2+ ⇤⇤ ⇤⇤ E. Klempt, 2019

I Test of quark models• Number of baryon states (frozen diquarks?)

Number of states rules out frozen diquarks,Cascade decays evidence 3-quark dynamics

• M2 / L + 2N (harmonic oscillator) or M2 / L + N (string models)

I Parity doublets• M(J+) = M(J�) ? unlikely!

Aims

I More baryons:Hyperons, cascades, charmed baryons, beautiful baryons

(D, LPN) S JP Singlet Octet Decuplet

(56, 0+0 ) 1

212+ N(939) ⇤(1116) ⌃(1193)

32

32+

�(1232) ⌃(1385)(70, 1�

1 ) 12

12�

⇤(1405) N(1535) ⇤(1670) ⌃(1620) �(1620) ⌃(1900)†32�

⇤(1520) N(1520) ⇤(1690) ⌃(1670) �(1700) ⌃(1910)†32

12� N(1650) ⇤(1800) ⌃(1750)

32� N(1700)

52� N(1675) ⇤(1830) ⌃(1775)

(56, 0+2 ) 1

212+ N(1440) ⇤(1600) ⌃(1660)

32

32+

�(1600) ⌃(1780)(70, 0+

2 ) 12

12+

⇤(1710) N(1710) ⇤(1810) ⌃(1880) �(1750) 32

32+

(56, 2+2 ) 1

232+ N(1720) ⇤(1890) ⌃(1940)

12

52+ N(1680) ⇤(1820) ⌃(1915)

32

12+

�(1910)32

32+

�(1920) ⌃(2080)32

52+

�(1905) ⌃(2070)32

72+

�(1950) ⌃(2030)

(70, 2+2 ) 1

232+

⇤(2070) 52+

⇤(2110) N(1860) �(2000) 32

12+ N(1880)

32+ N(1900)

52+ N(2000)

72+ N(1990) ⇤(2085)

(20, 1+2 ) 1

212+

32+

52+

(56, 1�3 ) 1

212� N(1895) ⇤(2000) ⌃(1900)†

32� N(1875) ⇤(2050) ⌃(1910)†

32

12�

�(1900) ⌃(2110)†32�

�(1940) ⌃(2010)†52�

�(1930) (70, 3�

3 ) 12

52�

⇤(2080) N(2060) 72�

⇤(2100) N(2190) ⌃(2100) �(2200)

I Are there “bumps” beyondthe quark model?

P0cs ! J/ N , N(1685 ! N⌘

⇤(1380)1/2� + ⇤(1405)1/2�

I Nature of “bumps”:

True resonance or rescattering?Factorization of prod. and decay

Quark-model state or dynami-cally generated resonances?Weinberg criterium

Caution:

(Baryon plus meson) and (qqq) can be different sets of wavefunctions. The true wave function is a superposition! There is noextra state, e.g. there is only one N(1535)1/2�.

Round table: Present and future of hadron spectroscopy

Feng-Kun GuoInstitute of Theoretical Physics, CAS

26 July – 1 Aug., 2021 1

Hidden-charm

2

Hidden-charm spectrum: One of the foci of hadron spectroscopy at present and in the near future

LHCb, PRL122,222001(2019)

Hidden-charm: spectrum to be corrected

3

z Many charmonium-like structures, some are close to thresholds, and the others do not. Any pattern?z In most cases, resonance parameters extracted using Breit-Wigner

� Coupled channels and thresholds not considered

Molecular spectrum predicted in X.-K. Dong, FKG, B.-S. Zou, Progr.Phys. 41 (2021) 65 [arXiv:2101.01021]

LHCb data: arXiv:2103.01803


4


� Unitarity: the same resonance may behave completely different in different processes

Line shapes of the same poles in different processesX.-K. Dong, FKG, B.-S. Zou, PRL126,152001(2021)

E.g., 𝑓𝑓0(980): peak in 𝐽𝐽/𝜓𝜓 → 𝜙𝜙𝜋𝜋+𝜋𝜋−, dip in 𝐽𝐽/𝜓𝜓 → 𝜔𝜔𝜋𝜋+𝜋𝜋−

BES, PLB607(2005)243 BES, PLB598(2004)149

𝐾𝐾�𝐾𝐾 → 𝜋𝜋𝜋𝜋 𝜋𝜋𝜋𝜋 → 𝜋𝜋𝜋𝜋


5

E.g., 𝑍𝑍𝑐𝑐𝑐𝑐(3985) @BESIII; 𝑍𝑍𝑐𝑐𝑐𝑐(4000, 4220) @LHCb

𝐷𝐷∗�𝐷𝐷𝑐𝑐∗𝐷𝐷𝑐𝑐 �𝐷𝐷∗,𝐷𝐷�𝐷𝐷𝑐𝑐∗

LHCb, arXiv: 2103.01803BESIII, PRL 126, 102001 (2021);talk by P.-G. Ping, Session-Exotics, 29.07

Ortega, Entem, Fernandez, 2103.07781;talk by Ortega, Session-Exotics, 28.07

dip


6


� Triangle singularities not considered

� Triangle singularities are sensitive to kinematic variables ⇒ energy dependence, more processes

� Narrow peaks for S-wave couplingReview: FKG, X.-H. Liu, S. Sakai, PPNP112, 103757 (2020)

Talks:• 𝑃𝑃𝑐𝑐 states:E. Swanson, Session-Exotics, 28.07;S. Nakamura, Session-Exotics, 28.07;

• In production of 𝑋𝑋 3872 :L. He, Session-Exotics, 28.07;

• 𝑑𝑑∗(2380):R. Molina, Session-baryon, 27.07;

• 𝑎𝑎1(1420):M. Wagner, Session-Exotics, 31.07;

• Structure at 𝑀𝑀𝑝𝑝𝑝𝑝 ≈ 1710 MeV:M. Nanova, Session-Baryon, 28.07;

• In 𝑝𝑝Σ− → 𝐾𝐾−𝑑𝑑:A. Feijoo Aliau, Session-Baryon, 31.07;…

Round table on “present and future of hadron spectroscopy” – lattice QCD

Christopher Thomas, University of Cambridge

19th International Conference on Hadron Spectroscopy and Structure (Hadron 2021), 26 July – 1 August 2021

[email protected]

1

• Precise results for low-lying (stable) hadrons in each flavour sector, physical quark masses, a → 0, isospin breaking (mu ≠ md and QED).

• Huge progress in using lattice QCD to study resonances etc in hadron-hadron scattering in the last decade.

• ρ resonance in (approximately) elastic ππ – many calculations by different groups, physical quark masses, a → 0.

• Other elastic scattering channels, e.g. Kπ, Dπ, DK

• Coupled-channel scattering, e.g. light scalars, b1, π1

[Plenary by Dave Wilson on Thursday and parallel talks]

Present and future – lattice QCD – 1

2

• Charmonium and bottomonium sector, “XYZ”s – very limited calculations so far.

• Exotic flavour: JP=1+ (I=0), bound states – charm analogues, resonances?

[Many parallel talks at Lattice 2021, e.g. Brian Colquhoun, Nilmani Mathur, Martin Pflaumer]

• Baryon-meson and baryon-baryon systems, e.g. Roper, Δ, deuteron, H dibaryon, Pc – so far conclusions less clear.

[Plenary by Ben Hörz at Lattice 2021]

• Glueballs?


3

• Formulation exists for 3-hadron scattering (for now some restrictions); so far only a few applications (e.g. I=3 πππ and I=3/2 KKK). Connection with experimental analyses.

[Plenary by Fernando Romero-Lopez on Thursday and parallel talks]

• Additional probes/tests from form factors and transitions. Formulation exists for resonances, very few applications.

• Lattice QCD can provide other interesting ways to probe the physics, e.g. by varying light-quark mass (mπ), SU(3)F symmetry.


� As for the exotic 𝜋𝜋1 on lattice, a �𝑞𝑞𝐺𝐺𝑞𝑞 operator is needed to get the correct mass, and it couplesstrongly to 𝑏𝑏1𝜋𝜋 [talk by D. Wilson, 29.07]; as for 𝑋𝑋(3872), both 𝑐𝑐𝑐𝑐 and 𝐷𝐷�𝐷𝐷∗ operators are needed [Prelovsek,Leskovec, PRL111, 192001, 2013]. On the other hand, the coupling contains structure information. How canwe learn about internal structure of the hadron states from such lattice information?

Questions

7

Taken from talk by P. Pauli, 29.07

�What is the dominant mechanism for 𝐽𝐽/𝜓𝜓 near-threshold production?1) Production mechanism in most literature assumed to be VMD2) The current reconciling the GlueX and LHCb results on 𝑃𝑃𝑐𝑐 relies on VMD,

leading to an upper limit of the 𝑃𝑃𝑐𝑐 → 𝐽𝐽/𝜓𝜓𝑝𝑝 branching fraction. If themechanism is different, the Br limits would be different.

GlueX data

GlueX, PRL123, 072001 (2019)M.-L. Du, V. Baru, FKG, C. Hanhart, U.-G. Meißner, A. Nefediev, I. Strakovsky, EPJC80(2020)1053

status of meson spectroscopy in the pdg · 2021. 8. 1. · 971.1± 4.0 28 aguilar-... 91 ehs 400 pp...

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