hadron physics with antiprotons with the panda experiment

Hadron Physics with Antiprotons with the PANDA Experiment at FAIR

Diego Bettoni INFN, Ferrara, Italy

Outline

•  Introduction •  Physics program •  PANDA at the MSV: the first 2 years •  Detector •  Summary

PANDA at FAIR D.Be.oni 2

One of the open problems in the Standard Model is a full understanding of Quantum Chromodynamics (QCD). QCD well and tested at high energies (perturbative regime). At low energies QCD becomes a strongly coupled theory, many aspects of which are not understood.

Physics Scope

PANDA at FAIR

Asympto7c freedom

Confinement

D.Be.oni 3

Experimental Measurements

•  Hadron Spectroscopy. Precision measurements of particle spectra to be compared with theory calculations. Identification of the relevant degrees of freedom. –  light quarks, cc, bb –  heavy-light systems (D and B mesons) –  baryons –  Search for new forms of hadronic matter: hybrids,

glueballs, multiquark states ... (X, Y, Z) •  Hadron structure.

–  Form Factors –  GDA, GPD, TMD –  Spin physics

•  Hadronic interactions: –  Hadrons in nuclear matter (Origin of mass) –  Hyperon physics (e.g. spin observables) –  Hypernuclei.


GSI Helmholtz Center and FAIR

PANDA at FAIR

p-‐Linac

HESR

SIS18 SIS100

CR/RESR

An7protons Produc7on Target

D.Be.oni 5

PANDA at FAIR

High luminosity mode High resolution mode

Nstored = 1010 p dp/p ~ 3×10-5 (electron cooling) Lumin. = 1031 cm-2 s-1

Nstored = 1011 p Lumin. = 2 x 1032 cm-2 s-1 dp/p ~ 10-4 (stochastic cooling)

Production rate 2x107/sec

Pbeam = 1.5 - 15 GeV/c Internal Target 4×1015 cm-2

High-Energy Storage Ring

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PANDA at FAIR

High luminosity mode High resolution mode

Nstored = 1010 p dp/p ~ 3×10-5 (electron cooling) Lumin. = 1031 cm-2 s-1

Nstored = 1011 p Lumin. = 2 x 1032 cm-2 s-1 dp/p ~ 10-4 (stochastic cooling)

Production rate 2x107/sec

Pbeam = 1.5 - 15 GeV/c Internal Target 4×1015 cm-2

High-Energy Storage Ring

Modularized Start Version (MSV0-3)

L ~ 1031cm-2s-1 Δp/p ~ 5 × 10-5

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PANDA at FAIR

pp Annihilation

Direct resonant formation of states with all non-exotic quantum numbers. ⟹ excellent precision in mass and

width measurement

Gluon- Rich Environment

Access to both exotic and non-exotic quantum numbers via production and formation reactions

Uniqueness of p probe (no other p facility in this energy range in the world)

Versatility of physics program (if coupled to universal detector)

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Comparison with Other Techniques

•  e+e-

–  direct formation limited to JPC = 1—

–  limited resolution for masses and widths for non vector states –  sub-MeV widths very difficult or impossible –  high L not accessible

•  high-energy (several TeV) hadroproduction –  high combinatorial background makes discovery of new states

very difficult –  width measurements limited by detector resolution

•  B decays (both for e+e- and hadroproduction) –  limited JPC

–  C cannot be determined since not conserved in weak decay


PANDA at FAIR

Experimental Method

( ) 4/412

22

2

2RR

RoutinBW ME

BBk

JΓ+−

Γ+=

πσ

The cross section for the process: pp → R → final state is given by the Breit-Wigner formula:

The production rate ν is a convolution of the BW cross section and the beam energy distribution function f(E,ΔE):

{ }∫ +Δ= bBW EEEdEfL σσεν )(),(0

The resonance mass MR, total width ΓR and product of branching ratios into the initial and final state BinBout can be extracted by measuring the formation rate for that resonance as a function of the cm energy E.

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PANDA at FAIR

Example: χc1 and χc2 scans in Fermilab E835

χ1

χ2

D.Be.oni 11

PANDA at FAIR

PANDA Physics Program •  HADRON SPECTROSCOPY

–  CHARMONIUM –  GLUONIC EXCITATIONS –  OPEN CHARM –  (MULTI)STRANGE BARYONS

•  NUCLEON STRUCTURE –  ELECTROMAGNETIC FORM

FACTORS –  TMDs –  GPDs, TDAs

•  HYPERNUCLEAR PHYSICS •  HADRONS IN THE NUCLEAR

MEDIUM

ArXiV:0903.3905 D.Be.oni 12

Exotic Hadrons I: Hybrids and Glueballs

p

p _

G

M

p

M

H

p _

p

M

H

p _

p

p _ G

p

p _ H

p

p _ H

Production

all JPC available

Formation

only selected JPC

nng ssg/ccg

PANDA at FAIR

Sound theoretical predictions from models and LQCD Gluon rich process creates gluonic excitation in a direct way Access to both exotic and non-exotic quantum numbers Highest precision for direct formation Access to both light and charm energy range UNIQUE to PANDA

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Glueball Search at PANDA


Exotic Hadrons II: X, Y, Z

PANDA at FAIR

BàK π+π-J/ψ

X(3872) Y(4260)

BaBar

Belle ψ’

X(3872)

Zc(3900) at BESIII

Need systematic approach with the capability to carry out high-precision measurements to map out completely the spectrum of these news states, in order to understand their nature: PANDA will be unique in achieving this.

D.Be.oni 15

X, Y, Z Rates at PANDA


X, Y, Z at PANDA


X(3872) at PANDA


Open Charm

•  QCD laboratory •  Intermediate case between heavy and light quarks •  Interesting spectroscopy •  Weak interactions At PANDA full program requires high luminosity (1032cm-2s-1). Unique features at PANDA: •  width measurement of DsJ(2317)

(30-100 KeV) (threshold scan) •  Access to high L (available in pp,

suppressed in B decays)


Strange and Charmed Hyperons


Strange and Charmed Baryons


Baryon Spectroscopy

PANDA at FAIR

•  New baryon states ? •  Properties of already known states. •  Symmetries in observed spectrum.

Baryons in PANDA •  Large cross section s for pp → YY

•  pp → ΞΞ ≈ µb •  pp → ΩΩ ≈ 0.002 ÷ 0.06 µb

•  No extra mesons in final state needed for strangeness or charm conservation •  Symmetry in hyperon and

antihyperon •  PANDA detector versatile

Prospects for PANDA

S=2 hyperons (Ξ) S=0 baryons (N) S=1 hyperons (Λ)

S=3 hyperons (Ω)

Charmed (Λc, Σc) Hidden charm (Ncc)

PANDA is a Strangeness Factory

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Spin Observables in Hyperon Production

PANDA at FAIR

The parity-violating weak decay of hyperons gives access to spin observables even for unpolarised beam/target. These observables give insight in the production mechanism of hyperons (e.g. the role of spin in strangeness and charm production). Unique to PANDA: the study of these observables and especially the hyperon-antihyperon spin correlations.

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Ξ- capture: Ξ- p → ΛΛ + 28 MeV

Ξ-

3 GeV/c

Kaons _Ξ

Λ Λ

trigger

p_

2. Slowing down and capture

of Ξ- in secondary

target nucleus

1. Hyperon-

antihyperon production

at threshold +28MeV

γ

3. γ-spectroscopy

with Ge-detectors

γ

Production of Double Hypernuclei

Ξ-(dss) p(uud) → Λ(uds) Λ(uds)

PANDA at FAIR

1300 Hz

8000 / month

80 / month

5600 / day 12C diamond target to produce Ξ− Trigger on Ξbar. Ξ− interacts with ac7ve target containing different nuclei. Detect decay products. •  High produc7on rate; •  Many hypernuclear systems at the same

7me; •  High acceptance/resolu7on magn. spect.

for neutral and charged; •  Ge-‐detectors for X-‐ray transi7ons;

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Charmonium in Nuclei

PANDA at FAIR

e+

e-

Measure J/ψ production cross section in p annihilation on nuclear targets. ⇒J/ψ-nucleus dissociation cross section

•  In PANDA the J/ψ is produced at relatively low energies. The cc pair hadronized in a very short time. •  Measurement problematic in pA (need to go to xF ≪ 0) •  ALICE at high energies opposite situation wrt PANDA.

PANDA produces charmonium in cold nuclear matter, providing exclusive information complementary to hadroproduction and heavy ion experiments.

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Proton Electromagnetic Form Factors in the Timelike Region

PANDA at FAIR

]2s [(GeV/c)4 6 8 10 12 14

R

0

0.5

1

1.5

2

2.5

3BaBar

LEAR

E835

FENICE+DM2

PANDA sim. I

PANDA sim. II

pp→ e+e− pp→ µ+−µ−

Measurement of effective form factor over wide q2 range (30 GeV2) Individual measurement of |𝐺𝐸| and |𝐺𝑀| and their ratio R First measurement of form factors with muons. Measurement of form factors in unphysical region Longer range goal: measurement of phase of |𝐺𝐸| and |𝐺𝑀| via polarisation observables.

pp→ e+e−π 0

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Drell-Yan Process at PANDA

PANDA at FAIR

Handbag diagram: s>>Mh2

PDFs are convoluted with the fragmenta7on func7ons

@ FAIR unique energy range up to s~30 GeV2 with PANDA @ much higher energies → big contribution from sea-quarks @ppbar annihilation each valence quark contribute to the diagram

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Transition Distribution Amplitudes

PANDA at FAIR

•  Describe the transition between two particles •  Explore pionic components in the nucleon wave function •  Transverse picture of the pion cloud •  Universality: the same TDA could be measured in different kinematics/reactions •  Test of Factorisation

D.Be.oni 30

PANDA at FAIR

Hard Exclusive Processes and pp→γγ Generalized Distribution Amplitudes (GDA)

The QCD factorization theorem allows us to calculate high energy cross sections separating short-distance process with long-distance non perturbative functions Hard scale is defined by the large transverse momentum of the final state photon

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Timelike wide-angle Compton scattering can be measured at PANDA S/B~1 for (25% efficiency) S/B~2 for (50% efficiency) Further studies are required for precise predictions

pp→ π 0γpp→ γγ

PANDA Spectrometer


Minimal Detector for Start Physics

•  Target TDR approved ✔ •  Charged track detection and momentum

–  Magnets TDR approved ✔ –  MVD TDR approved ✔ –  STT Tracker TDR approved ✔ –  Forward tracker (2/6) TDR 2016 –  Muon chambers TDR approved ✔

•  Photons and electrons –  Electromagnetic calorimeter TDR approved ✔ –  Shashlyk TDR submitted

•  Particle ID –  Barrel DIRC TDR 2016 –  Forward TOF TDR 2016


Cluster Solenoid Muon GEM Dipole Muon Range Luminosity Target Detectors Plane System Detector

Barrel DIRC MVD STT Barrel FE Part FToF FSC EMC EMC F-Trk

BE EMC

PANDA Start Setup


Cluster Solenoid Muon GEM Dipole Muon Range Luminosity & Pellet Detectors Tracker System Detector

Target

Barrel DIRC MVD STT Barrel Disc FE Full FRICH FToF FSC Barrel ToF EMC DIRC EMC F-Trk

BE EMC

PANDA Final Setup


Summary

•  PANDA has developed a world class experimental program covering the three pillars of hadron physics: –  hadron spectroscopy –  hadron structure –  hadron interaction These experimental programs present many synergies and can in most cases be carried out in parallel.

•  PANDA is unique in combining the potential for the discovery of new physics with the ability to carry out precise, systematic measurements.

•  This physics potential will remain intact, and even increase, with time.

•  The collaboration, detector developments and funding are in good shape and we are on track to produce excellent physics at the beginning of the next decade.


hadron physics with antiprotons with the panda experiment

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