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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. Evidence for a Higgs particle in CMS Is it Peter´s Higgs or just a Higgs? What it has to do with the “origin of mass” in the universe?

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slide1

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
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
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
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
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)

cms collaboration
CMS Collaboration

1400 Physicists

600 Graduate students

175 Institutes

38 Countries

assembly in the surface hall
Assembly in the surface hall

Waiting for the cavern to be ready

heart of cms all silicon tracker 200 m 2
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.

dimuon mass resolution
Dimuonmassresolution

24 yearsofe+e- machines

24 hoursof LHC

lhc luminosity
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
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
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 branching ratios
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 branching ratios1
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 andalreadyappreciable! (golden, sincetheyshownarrow invariant

masspeakwithwidth limited by experimental resolution)

searching for the higgs in the four leptons final state
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
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

december 2012 data
December 2012 data

Significance 4.5 s

Mass 126.2 ± 0.6 (stat) ± 0.2 (syst) GeV

search for the sm higgs boson in the gg channel
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/E1sE2/E2cot(q/2)Dq]

Target for the intercalibration < 0.5%

mass resolution of gg system find the right vertex
Mass resolution of gg system: Find the right vertex

g1

g2

sm/m = 0.5 [sE1/E1sE2/E2cot(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
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

outline1
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
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 spin parity
A first glimpse at SpinParity
  • Spin 0  2 S=1 particles
  • angular correlations.
  • Positive parity 12 allowed 
  • decay planes aligned.
  • Negative parity12allowed
  • decay planes orthogonal

in favour of 0+ !

p(0–) = 0.072

p(0+) = 0.72

So spin and parity consistent with Peter’s Higgs

fit of generalized couplings
Fit of generalized couplings

So couplings consistent

with Peter’s Higgs

outline2
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?
slide33

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

slide34

The giganticdarkenergyproblem

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???

outline3
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?
what is the higgs boson good for
Whatisthe Higgs bosongoodfor?

Answer: without Higgs fieldwewould not exist!

E.g.

Itgivesmasstotheelectron: withoutelectronmassnoatoms (r1/me)

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

outline4
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?
what is so special about the higgs boson
Whatis so specialaboutthe Higgs boson?

Higgs massbelow 130 GeV,

as PREDICTED by SUSY!

W. Hollik: formetheobserved Higgs bosonwith a massconsistent

withSupersymmetryisthestrongesthintforSupersymmetry!

slide39

Other beautiful SUSY features

  • SUSYprovides UNIFICATION ofgaugecouplings
  • SUSYprovides UNIFICATION of Yukawa couplings
  • SUSYhasnoquadraticdivergenciesHiggs mass
  • canbecalculateduptounificationscale
  • SUSYpredicts EWSB withlightest Higgsbelow 130 GeV
  • LHC: Mh= 126 GeV
  • SUSYprovides„dark matter miracles“:
  • Neutralinoannihilation x-section a fewpb
  • correctrelicdensity
  • Neutralino-nucleonscatteringcrosssection
  • < 10-8pbconsistentwith experimental limits
slide40

Unificationfor TeV SUSY masses

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

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

iaregaugecouplingsof SU(3)SU(2)LU(1)

(in first order i  1/log (energy Q)

slide41

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)

slide42

NMSSM solves-problem

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

MSSM

NMSSM

slide43

Higgs mass in MSSM and 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

slide44

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 bbarbbartot hardlyeffected, aslongasbbar  tot
  • Higgs withlargestsingletcomponentusuallylightestone. Sinceithassmallcouplingsto SM particles, itis NOT excludedby LEP limit.
slide45

Status of NMSSM

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 h3h2+h1

slide46

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
slide47

Allowedparameterspace

LEP

Xenon

+MA

LHC

Bs

slide53

Summary

  • 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
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