the discovery of the brout-englert-higgs boson and its ...ekpdeboer/html/talks/ow_2014.pdfgiving...

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

Institut für Experimentelle Kernphysik

www.kit.edu

The Discovery of the Brout-Englert-Higgs Boson1

and its Implications for Supersymmetry and Cosmology

Wim de Boer, KIT (update from arxiv1309.0721)

1Shortened to Higgs Boson in what follows

2 Wim de Boer New Physics Within and Beyond the Standard Model 571. WE-Heraeus-Seminar, Oberwölz, Austria, Sept. 2014

The Mass Problem (solution proposed PRL 16.11.1964)

!   SM = relativistic quantum field theory based on local gauge symmetries !   BUT: local gauge symmetries incompatible with mass (mass = 0 for chiral fermions and gauge bosons) !   1962: Schwinger proposed that masses can be generated dynamically by

interactions with a vacuum field !   Problem: Goldstone theorem predicted massless bosons after spontaneous

symmetry breaking, but these were not observed !   1963 Anderson applied idea to superconductivity and postulated that

Goldstone bosons become longitudinal degrees of freedom of the „plasmons“ !   1964 Higgs applied the idea of Anderson to relativistic gauge bosons !   1964 Brout and Englert showed that spontaneous symmetry breaking gives

mass to gauge bosons (but did not discuss the Goldstone boson problem) !   1964 Guralnik, Hagen, and Kibble showed in a model that the Goldstone

theorem is not applicable after breaking a symmetry locally !   2012: Brout-Englert-Higgs-Guralnik-Hagen-Kibble Boson discovered


Predicted Properties of the Higgs Boson

Idea: Higgs field gives mass to electroweak gauge bosons W,Z, and not to photon and gluon, by INTERACTIONS.

Giving mass means slowing down: E2= p2 +m2 and β≡ v/c =p/E, so if m=0 then β≡1 and if m>0 then β<1. (Like photon getting mass, if it enters superconductor by interactions with the Cooper pairs or classically, a diver is slowed down by the interaction with the water and the quanta of the water „field“ are H2O molecules, just like quanta of the Higgs field are the Higgs bosons.

Strong predictions: § Higgs field must have weak isospin (to couple to W,Z) § Must be electrically neutral (not to interact with the photon) § Must have spin 0 with positive parity (no preferred direction in

vacuum) § Particle masses proportional to couplings to the Higgs boson


Outline

§  Discovery of a Higgs particle

§  Implications for Cosmology

§  Implications for Supersymmetry

Details in https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HiggsPublicResults https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsHIG K.A. Olive et al. (Particle Data Group), Chin. Phys. C38, 090001 (2014). W. de Boer, arXiv:1309.0721


The LHC

≈ 2000 superconducting magnets at -271.3 0C (1.9K) in 120 tonnes of liquid He 26,7 km circumference max. 2808 proton bunches, 40 MHZ collision rate, ~1011 Protons / bunch

~500 million pp collisions / s at 7 & 8 TeV centre of mass energy

Bending magnets

Cavities for acceleration


LHC: broad range of CM energies and high luminosity

(1 day LHC)


10-1 100 101 102 103

E [GeV]

10-37

10-35

10-33

10-31

10-29

Cro

ss s

ectio

n [c

m2 ]

u,d s

c

b

WW + ZZ

µ+µ-

J/ψ ϕ ρ/ω

Υ Z

24 years of e+e- colliders


LHC Run I Luminosity

Both general purpose detectors (ATLAS, CMS) collected about 25 1/fb

Higgs discovery

Higgs discovery


History of Discovery PDB

Summer 2011: EPS, first LHC Data

December 2011: Cern Council, first hints

Summer 2012: ICHEP, discovery

December 2012: End of Run I, Start of new era

PDB, shown by Kado


Higgs branching ratios

§  bb dominates below WW threshold.

§  ττ is down by ~ 9 due to coupling to mass, and 1/3 color factor.

§  WW factor two higher than ZZ because distinguishable particles

§ In addition phase space.

We are lucky with MH=125 GeV: bb down to 57 % and „golden“ channels ZZ->4l (3%) and γγ (0.2%) already appreciable! (golden, since they show narrow invariant mass peaks, because no neutrinos in the decay)


Historic moment (July 4th, 2012)


CERN July 4th Seminar, 2012 Summary from CMS by Joe Incandela: We have observed a new boson with a mass of 125.3 ± 0.6 GeV at 4.9 σ significance ! Summary (excerpt) from ATLAS by Fabiola Gianotti: We observe an excess of events at m_H ~ 126.5 GeV with local significance 5.0 sigma Remarks from the CERN Director General Rolf Heuer: “As a layman I would now say I think we have it. Do you agree?” Michel Spiro (President of CERN Council): “If I may say so it is another giant leap for mankind.” Chris Llewellyn Smith (former DG): “I really am amazed that we can use these luminosities.” Francois Englert: “I am extraordinary impressed by what you have done.” Peter Higgs: “It is an incredible thing that it has happened in my lifetime.” Gerald Guralnik: “It is wonderful to be at a physics event where there is applause like there is at a football game.” Rolf Heuer: “Everybody that was involved in the project can be proud of this day. Enjoy it.” From: http://www.quantumdiaries.org/author/jim-rohlf/


78 reconstructed vertices in high pile-up run


2013 Nobel prize for François Englert and Peter Higgs


Higgs Production at the LHC

„gluon fusion“

„vector boson fusion“

„vector boson radiation“

„tt associated production“

Rate @ 8 TeV 25-50% higher than7 TeV


Higgs background channels

Higgs x-section ≈ VV x-section


The Standard Model agrees with experiment


Golden Channel I: H -> Diphoton

arXiv:1408.7084

µ: 1.14 ± 0.21(stat) ± 0.16(sys)

5.2 σ

was 1.6±0.3 with 7.3 σ

5.7σ

µ: 1.17 ± 0.23(stat) ± 0.16(sys)

arXiv:1407.0558


Golden Channel II: H->ZZ*->4l

arXiv:1312.5353,PRD

6.8 σ

µ: 0.93 ± 0.25(stat) ± 0.11(sys)

arXiv:1408.5191

8.1σ

µ: 1.50 ± 0.33(stat) ± 0.12(sys)


Higgs Mass

ATLAS-HIGG-2013-12

Higgs mass: 125.03 ± 0.30 GeV Higgs mass: 125.36 ± 0.41 GeV

CMS-PAS-HIG-14-009


A first glimpse at SpinParity

§  S=0 ⇒ two S=1 particles ⇒ decay angles depend on parity

§  Positive parity ⇒  ε1•ε2 allowed ⇒ decay planes aligned.

§  Negative parity ⇒  ε1×ε2 allowed ⇒ decay planes orthogonal

Study angular correlations in HèZZè4l

arXiv:1001.3396

red=0+

blue=0-


1212.6639 1307.1432

Both experiments in favour of 0+ ! (Prob. for 0– : 2.2%)

Spin and Parity consistent with SM Higgs


Higgs Couplings proportional to Mass


Most wanted Answer in 2013: Does the Higgs couple to fermions?


ATLAS: ττ + bb → 3.7 σ CMS: ττ + bb → 3.8 σ

Strong evidence for coupling to fermions

ATLAS-CONF-2014-009 CMS-HIG-13-033, Nature Phys. 10(2014)


Higgs and Cosmology

@NASA

The „complete“ SM describes only 4.6% of the energy in our universe.

We know it is only 4.6% from ratio of photons/baryons≈1010

which determines ratio heavy/light nuclei and CMB acoustic peaks (photons: 412/cm3 everywhere for a CMB temperature of 2.7 K)

The dark side divided in two classes: Dark Matter with attractive gravity Dark Energy with repulsive gravity (Nobel prize 2011)

Repulsive gravity is caused by a constant energy density, like vacuum energy (Higgs field?) or a cosmological constant


Separation of DM and DE (Λ)

ΩMatter = 0.3

ΩΛ =

0.7

Perlmutter,Schmidt and Ries got NP for measuring acceleration of universe prop. to a ≈ ΩΛ-ΩM

Mather and Smoot got NP for measuring CMB anisotropy which later revealed that the universe is flat or 1 ≈ ΩΛ+ ΩM

Combining results of the two orthogonal graphs yields ΩM = 0.3, ΩDE = 0.7


Time evolution of Universe

Cosmology badly needs evidence for symmetry breaking via scalar field. Idea: High vacuum density of such a scalar field in early universe during breaking of GUT would provide a burst of inflation by „repulsive“ gravity. Otherwise no explanation why the universe has matter, is flat and is isotropic. Discovery of Higgs field as origin of ewsb important


The gigantic dark energy problem

V(φ=φ0) = -mH2mW

2/2g2

= O(108 GeV4) = 1026 g/cm3

1 GeV4=(GeV/c2 )(GeV3/(ħc)3) = 10-24 g 1042 cm-3 = 1018 g/cm3

Average density in universe: ρcrit = 2 x 10-29 g/cm3

Problem: Vacuum energy of Higgs field estimated to be 55-120 orders of magnitude larger than observed density. WHY IS THE UNIVERSE SO EMPTY??? Did EWSB provide another burst of inflation, thus diluting energy density of Higgs field??


Is Higgs Field the „Origin of Mass“?

Answer: Yes and No. Energy or mass in Universe has little to do with the Higgs field. Higgs field gives only mass to elementary particles. Mass in universe: 1)  Atoms: most of mass from binding energy of quarks in nuclei,

provided by energy in colour field, not Higgs field. (binding energy ≈ potential energy of quarks ≈ kinetic

energie of quarks, ca. 1 GeV, but mass of u,d quarks below 1 MeV! 2) Mass of dark matter: unknown, but in Supersymmetry by breaking of this symmetry, not by breaking of electroweak symmetry.


What is known about DM?

In blob: only Z or Higgs particles to explain neutral and weak interactions But 9 orders of magnitude between I and II most easily explained by Higgs exchange, since Higgs couples only weakly to light quarks Need DM as singlet, so little coupling to Z ->Higgs Portal models: in III Higgs is Portal between visible and invisible sector! (see Kanemura, Matsumoto,Nabeshima, Okada arXiv:1005.5651) SUSY with singlet Higgs: NMSSM (DM = „singlino-like“) Or DM bino-like neutralino, which does not couple to Z either (MSSM)

DM DM

p p

σ  < 10-8 pb from direct DM searches

I DM

DM

p

p

σ  < 10-8 pb DM from tag by Z or monojet

(Z-tag less bg, more sens.)

III DM

DM

p,b

p,b

σ  ≈ 10 pb from relic density Ω

(assuming thermal relic)

II

x

x


Higgs invisible Width in Higgs Portal Models

1402.3244

Search for: pp-> ZH->2l+Emiss pp-> ZH->2b+Emiss pp-> qqH->2q+Emiss

1404.1344

Upper limit on invisible width: 2-3 MeV for DM mass < MH/2


Direct Upper Limit on Higgs Width

! Higgs Portal: DM may change Higgs width ! Unfortunately: exp. resolution (3-4 GeV) >> SM width (4 MeV) !   Trick to improve: compare on- and off resonance (Caola,Melnikov,1307.4935) !   Idea is simple:

dominant on-resonance

dominant off-resonance

Upper limit on width: 22 MeV

arXiv:1405.3455 ATLAS-CONF-2014-042


What is so special about the Higgs boson?

Higgs mass IS below 130 GeV, as PREDICTED by SUSY!

§  SUSY provides UNIFICATION of gauge couplings

§  SUSY provides UNIFICATION of Yukawa couplings

§  SUSY predicted EWSB for 140 < Mtop < 190 GeV

§  SUSY provides WIMP Miracle: annihilation x-section -> correct relic density

§  SUSY solves hierarchy problem

§  SUSY provided connection with gravity


Where to find SUSY masses? U

. Am

aldi

, WdB

, H. F

ürst

enau

, PLB

, 199

1,

αi are gauge couplings of SU(3)⊗SU(2)L⊗U(1) Unification for SUSY scale in 0.5-5 TeV range


Present and future LHC sensitivities

Gluino sensitivity

Now: 1200 GeV

Exp. for 3000/fb at 14 TeV 3000 GeV

1308.1333


Gluino

Chargino

Neutralino

Radiative corrections to gauginos

Weakly interacting particles have only weak radiative corrections so charginos and neutralinos naturally lighter than gluinos


Where is SUSY?

Remind: Chargino/gluino ≈ 1/3 from radiative corrections Gluino limit of 1200 GeV èchargino limit of 400 GeV Weak cross section are weak: Observed at LHC: 250 WZ pairs (into leptons) Expect: WinoZino pairs with masses 5x as large: 250/5^4= 1/3 of an event. NEED MUCH MORE LUMI before deciding SUSY is dead. Expect to reach 1 TeV limit only after HL-LHC ≈ 2030 (3000/fb)


LHC 14 3000 /fb not sens.

Higgs+Ω allowed

Higgs 125 allowed

CMSSM NMSSM

Answer: depends on model, see e.g arXiv:1402.4650 Who can see DM first? LHC or direct DM Searches

LHC better for CMSSM (WIMP mass related to gluino mass by rad. corr.)

Direct DM searches better for NMSSM (WIMP mass indep. of SUSY masses, since singlino)


NMSSM 1) solves µ-problem (µ parameter =vev of singlet, so naturally small)

2) predicts naturally Mh>MZ, so no need for radiative corrections from multi-TeV stop masses. Many papers since discovery of 125 GeV Higgs, see e.g. arXiv:1408.1120, arXiv:1407:4134, arXiv:1407.0955, arXiv:1406.7221, arXiv:1406.6372, arXiv:1405.6647, arXiv:1405.5330, arXiv:1405.3321, arXiv:1405.1152, arXiv:1404.1053, arXiv:1403.1561, arXiv:1402.3522, arXiv:1401.1878, arXiv:1312.4788, arXiv:1311.7260, arXiv:1310.8129, arXiv:1310.4518, arXiv:1309.4939, arXiv:1309.1665, arXiv:1405.5330, arXiv:1308.4447, arXiv:1308.4447, arXiv:1308.1333, arXiv:1307.7601, arXiv:1307.0851, arXiv:1306.5541, arXiv:1306.3926, arXiv:1306.3646, arXiv:1306.0279, arXiv:1305.3214, arXiv:1305.0591, arXiv:1305.0166, arXiv:1304.5437, arXiv:1304.3670, arXiv:1304.3182, arXiv:1303.6465, arXiv:1303.2113, arXiv:1303.1900, arXiv:1301.7584, arXiv:1301.6437, arXiv:1301.1325, arXiv:1301.0453, arXiv:1212.5243, arXiv:1211.5074, arXiv:1211.1693, arXiv:1211.0875, arXiv:1209.5984, arXiv:1209.2115, arXiv:1208.2555, arXiv:1207.1545, arXiv:1206.6806, arXiv:1206.1470, arXiv:1205.2486, arXiv:1205.1683, arXiv:1203.5048, arXiv:1203.3446, arXiv:1202.5821, arXiv:1201.2671, arXiv:1201.0982, arXiv:1112.3548, arXiv:1111.4952, arXiv:1109.1735, arXiv:1108.0595, arXiv:1106.1599, arXiv:1105.4191, arXiv:1104.1754, arXiv:1101.1137,

Status of NMSSM


Higgs mass in MSSM and NMSSM

MSSM

Higgs mass in MSSM ≈125 GeV for mstop ≈ 3 TeV

NMSSM: mixing with singlet

increases Higgs mass at TREE level for small tanβ and large λ NO MULTI-TEV stops needed

WDB et al., arXiv:1308.1333


Branching ratios in NMSSM may differ from SM

§  Total width of 125 GeV Higgs Γtot may be reduced somewhat by mixing with singlet (singlet component does not couple to SM particles) and new decay modes, like H3èH2+H1

§  Mixing depends on unknown masses, so deviations not

precisely known. Expect O(<10%) deviations.

§  Higgs with largest singlet component usually lightest one. Since it has small couplings to SM particles, it is NOT excluded by LEP limit. Dark Matter candidate is Singlino instead of BINO in MSSM. Singlino mass typically 30-100 GeV.


Lightest singlet Higgs at LEP?

NMSSM consistent with H1=98 GeV, H2=126 GeV, motivated by 2σ excess observed at LEP at 98 GeV with signal strength well below SM. (Belanger, Ellwanger, Gunion, Yian, Kraml, Schwarz,arXiv:1210.1976) H1 hard to discover at LHC, may be in decay mode H3⇒H2+H1 , see e.g. Kang, Li, Li, Shu, arxiv:1301.0453

114.3

2σ

Ale

ph, D

elph

i, L3

, Opa

l P

hys.

Let

t. B

565

(200

3) 6

1


Expected coupling precision (SM)


Summary

§  Higgs boson with mass of 125 GeV well established

§  All properties (Br and Spin) consistent with SM Higgs boson

§  Higgs hunt not over, since mass in range expected from Supersymmetry, which predicts more Higgs bosons. NMSSM does not need multi-TeV stops.

§  Like to see branching ratios at level of a few % to check

possible deviations from SM, as expected in NMSSM

§  Looking forward to LHC at higher energies, ILC, dark matter searches

the discovery of the brout-englert-higgs boson and its ...ekpdeboer/html/talks/ow_2014.pdfgiving...

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