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CMS Observation of a new boson at the LHC and its implications for the origin of mass.

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CMS Observation of a new boson at the LHC and its implications for the origin of mass.

Wim de Boer (for the CMS Collaboration)

Outline

- Evidencefor a Higgs particle in CMS
- Is itPeter´s Higgs or just a Higgs?
- What it has to do with the “origin of mass” in the universe?
- What is the Higgs boson good for?
- What is so special about observed Higgs particle?

The LHC

Two rings with 1232superconducting dipoles

and 858 quadrupoles,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

Bendingmagnets

Cavitiesforacceleration

Design Criteria for the CMS Experiment

First conceptual design of a “Compact Muon Solenoid” (CMS) was presented in Aachen (1990) based on a 4 Tesla solenoid.

- Very good muon identification and momentum measurement.
- H® ZZ, with Z®mm
- Most precise photon detector.
- H®gg
- Powerful inner tracking for electron identification.
- H®ZZ, Z®ee
- Hermetic calorimetry for missing ET signatures: H®WW, W® mn

From M. Della Negra, Wess-prizerecipient (with P. Jenny), 2013, Karlsruhe

Compact Muon Solenoid (CMS) Experiment

3.8 T Magnet

Bend tracks of charged particles

Calorimeters

Absorb particles and measure their energy

Silicon Detectors

Measure tracks left by charged particles

Muon Detectors

Identify and measure muons that penetrate

z

0 (center)

Assembly in the surface hall

Waiting for the cavern to be ready

Heart of CMS: all silicon tracker (200 m2!)

Pile-up: many collisions pro bunch crossing

66 million silicon pixels: 100 150 µm2

9.3 million silicon microstrips: 80µm - 180µm.

~200 m2 of active silicon area (cf ~ 2m2 in LEP detectors)

~13 precise position measurements (15 µm ) per track.

LHC Luminosity

New records:–centre-of-mass energy 8 TeV

– peak luminosity 0.77∙ 1034 / cm² /sec – best week ∫L=1.35 fb-1

( 75% design luminosity @ half energy & half # of bunches)

(delivered)

TAM 2013

HCP 2012

summer

conferences 2012

pp processes in Standard Model

9 ordersofmagnitude: 1 in a billion

7 14 TeV

Higgs events are rare !

Need 5x more lumi at 14 TeV

to discover 500 GeV Higgs

Higgs Production at the LHC

„gluon fusion“

„vector boson

fusion“

„vector boson

radiation“

„tt associated

produktion“

Rate @ 8 TeV 25-50% higher than7 TeV

Higgs branchingratios

Note that q,l width ~ M while W,Z width ~ M3. Hence bb dominates below WW “threshold”. is down by ~ 9 due to coupling to mass, and 1/3 color factor.

Higgs branchingratios

- bb dominates below WW threshold.
- is down by ~ 9 due to coupling to mass, and 1/3 color factor.
- WW higher than ZZ because distinguisable particles:
- In addition phase space.

Weare lucky withMh=126 GeV: bb down to 60 % and „golden“ channels

ZZ->4l andalreadyappreciable! (golden, sincetheyshownarrow invariant

masspeakwithwidth limited by experimental resolution)

Searching for the Higgs in the four leptons final state

For a low mass Higgs the fourth lepton is soft.

Selection cuts:

Electrons pT > 7 GeV

MuonspT > 5 GeV

40 GeV < m12 < 120 GeV

m34 > 12 GeV

H ® ZZ ® 4 leptons

6

7

Expected: BG:9.4, SIGNAL: 18.6 Total: 28

Observed: 25Signal strength: 0.9 0.3

Significance 6.7 s(7.2 s exp)

Mass: 125.8 ± 0.5 (stat) ± 0.2 (syst) GeV

Search for the SM Higgs boson in the gg channel

Mass resolution is the key for Higgs discovery in this channel

H®gg Simulation (100 fb-1)

PbWO4 crystals

Test Beam October 2003

sm/m = 0.5 [sE1/E1sE2/E2cot(q/2)Dq]

Target for the intercalibration < 0.5%

Mass resolution of gg system: Find the right vertex

g1

g2

sm/m = 0.5 [sE1/E1sE2/E2cot(q/2)Dq]

Need vertex to betterthan 10 mm, bunch 50 mm

- Algorithm to find the right vertex based on SpT2 of tracks and pTgg balance.
- Tested on Z®mmevents by treating muons as gammas.
- Overall efficiency to find the right vertex for Higgs (m = 120 GeV) integrated
- over pT spectrum: ~ 80%

gg Mass Distribution

Background is estimated from the data by a polynomial fit.

An excess is observed consistent with a narrow resonance around

125 GeV mass at 4.1 s

Outline

- Evidencefor a Higgs particle in CMS
- Is itPeter´s Higgs or just a Higgs?
- What it has to do with the “origin of mass” in the universe?
- What is the Higgs boson good for?
- What is so special about observed Higgs particle?

Other Channels

- Search for the Higgs in other decay modes : WW, bb and tt
- Combined significance at MH=125.8 GeV: 6.9 s
- Overall satisfactory level of compatibility withthe SM cross section.
- Combined s/sSM= 0.88 ± 0.21 (so signal consistent with Peter’s Higgs)

A first glimpse at SpinParity

- Spin 0 2 S=1 particles
- angular correlations.
- Positive parity 12 allowed
- decay planes aligned.
- Negative parity12allowed
- decay planes orthogonal

in favour of 0+ !

p(0–) = 0.072

p(0+) = 0.72

So spin and parity consistent with Peter’s Higgs

Outline

- Evidencefor a Higgs particle in CMS
- Is itPeter´s Higgs or just a Higgs?
- What it has to do with the “origin of mass” in the universe?
- What is the Higgs boson good for?
- What is so special about observed Higgs particle?

Is Higgs Field the „Origin ofMass“?

Answer: YesandNo. Energyormass in Universehaslittleto do with Higgs field. Higgs fieldgivesonlyelementaryparticlesmass.

Mass in universe:

Atoms: mostofmassfrombindingenergyofquarks in nuclei, providedbyenergy in colourfield, not Higgs field.(bindingenergy

potential energyofquarks kinetic

energieofquarks, ca. 1 GeV,

massofu,dquarksbelow1 MeV!)

2) Massofdarkmatter: unknown, but in Supersymmetrybybreakingofthissymmetry, not bybreakingofelectroweaksymmetry.

Dark energy: Higgs energydensityseemstoo large. Why?Giganticproblem!

darkenergy= 0.7

matter = 0.3

Acceleratedexpansionofuniverseimplies a constantenergydensity in space time, either a cosmologicalconstantorsomekindofvacuumenergy. The Higgs fieldisthoughtofaspermeatingspace time with a constantenergydensity, whichcanbeeasilyestimatedfromtheeffective potential tobe 55 ordersofmagnitudeabovethedarkenergydensityofabout 10-29 g/cm3

Ifzero-pointfluctuationsoffieldconsideredandintegratedto Planck scale, problemevenmoresevere: (1018)4 GeV4 = 120 ordersofmagnitude larger thanthedarkenergydensity

In Supersymmetryproblemsomewhatless, sinceabovebreakingscalefermionsandbosons cancel in zero-pointfluctuations,

problem„only“ 60 ordersofmagnitude.

V(=0) = -mH2mW2/2g2

= O(108 GeV4) = 1026 g/cm3

1 GeV4=(GeV/c2 )(GeV3/(ħc)3)

= 10-24 g 1042 cm-3 = 1018 g/cm3

Averagedensity in universe:

crit= 2.10-29 g/cm3

WHY IS THE UNIVERSE

SO EMPTY???

Outline

- Evidencefor a Higgs particle in CMS
- Is itPeter´s Higgs or just a Higgs?
- What it has to do with the “origin of mass” in the universe?
- What is the Higgs boson good for?
- What is so special about observed Higgs particle?
- Does the observation point to physics beyond the Standard Model?

Whatisthe Higgs bosongoodfor?

Answer: without Higgs fieldwewould not exist!

E.g.

Itgivesmasstotheelectron: withoutelectronmassnoatoms (r1/me)

Itgivesmasstothe W,Z bosons, whichmakeweakinteractionsweakatlowenergy, so thesunshinesfor 8 billionyears

Outline

- Evidencefor a Higgs particle in CMS
- Is itPeter´s Higgs or just a Higgs?
- What it has to do with the “origin of mass” in the universe?
- What is the Higgs boson good for?
- What is so special about the observed Higgs particle?

Whatis so specialaboutthe Higgs boson?

Higgs massbelow 130 GeV,

as PREDICTED by SUSY!

W. Hollik: formetheobserved Higgs bosonwith a massconsistent

withSupersymmetryisthestrongesthintforSupersymmetry!

- SUSYprovides UNIFICATION ofgaugecouplings

- SUSYprovides UNIFICATION of Yukawa couplings

- SUSYhasnoquadraticdivergenciesHiggs mass
- canbecalculateduptounificationscale

- SUSYpredicts EWSB withlightest Higgsbelow 130 GeV
- LHC: Mh= 126 GeV

- SUSYprovides„dark matter miracles“:
- Neutralinoannihilation x-section a fewpb
- correctrelicdensity
- Neutralino-nucleonscatteringcrosssection
- < 10-8pbconsistentwith experimental limits

Unificationfor TeV SUSY masses

U. Amaldi, WdB, H. Fürstenau, PLB, 1991,

wdb. C, Sander, PLB 2004, hep-ph/0307049

iaregaugecouplingsof SU(3)SU(2)LU(1)

(in first order i 1/log (energy Q)

Higgs mechanismuspredicted in SUSY

Common masses at GUT scale:

m0for scalars

m1/2for S=1/2 gauginos

m1,m2for Higgs bosons

m2driven negative by top loops ,

electroweak symmetry breaking

at MZfor 140<Mt<200 GeV!

BINGO, Mtop predicted in this range

by SUSY and it was found at

171 ± 1.3 GeV!

EWSB only works if starting point at GUT scalenot too large:

need EW scale, but it is term

of supersymm. potential, could be

GUT scale (-problem)

<S> is termofMSSM. If isvevfromsinglet S, noproblemtobesmall. Now3 scalar Higgs bosons! (and 2 pseudoscalar)

MSSM

NMSSM

MSSM

Higgs mass in MSSM 125 GeV

formstop 3TeV

NMSSM: mixingwithsinglet

increases Higgs massat BORN level

forsmall tan and large

NO MULTI-TEV stopsneeded

Branchingratios in NMSSM maydifferfrom SM

- Total widthof 126 GeV Higgs totmaybereducedsomewhatbymixingwithsinglet(singletcomponentdoes not coupleto SM particles).
- Thenbranchingratiosenhanced, e.g.
- BR(H tot enhanced (enhancementmaybereducedbylightstopsatgluonfusionloopby neg. interferencewith top loops)
- Main decaymode BR(H bbarbbartot hardlyeffected, aslongasbbar tot
- Higgs withlargestsingletcomponentusuallylightestone. Sinceithassmallcouplingsto SM particles, itis NOT excludedby LEP limit.

Manypapers on NMSSM after Mh=126 GeV and

hintoftoohighBrinto, seearXiv: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, arXiv:1012.4490, ………..

NMSSM consistentwith h1=95 GeV, h2=126 GeV, motivatedby 2 excessobservedat LEP at 95 GeV withsignalstrength 2 well below SM.

Hardtodiscoverat LHC, maybe in

decaymode h3h2+h1

Determining allowed SUSY parameter range

Variables calculated with

NMSSMTools 3.2.4 using

Ulrich Ellwanger*, John F. Gunion**, Cyril Hugonie***

http://www.th.u-psud.fr/NMHDECAY/nmssmtools.html

MicrOMEGAs 2.4.1

G. Bélanger, F. Boudjema, P. Brun, A. Pukhov,

S. Rosier-Lees, P. Salati, A. Semenov

http://lapth.in2p3.fr/micromegas/

Minuit for minimization

These dominate

parameterspace

- LHC limits on squarksandgluinos.
- Mh=126 GeV

- Higgs bosonat 126 GeV well established
- All properties (Brand Spin) consistentwith SM Higgs boson
- Higgs hunt not over, sincemass in rangeexpectedfromSupersymmetry, whichpredictsmore Higgs bosons
- Hopefully a Higgs comesseldomalone
- Need Bratlevelof a few % to check possibledeviationsexpected in NMSSM

From Concept to Data Taking: 18 years

Letter of Intent (1992)

Technical Proposal (1995)

10 Technical Design Reports (1997-2006)

3000 scientists from 40 countries

Hermetic electromagnetic calorimeter

Scintillating Crystals

Silicon Tracker

CMS cut in mid-plane

Muon Chambers

Hermetic Hadron Calori-meter: Brass scintillator

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