Higgs Physics at the Large Hadron Collider Markus Schumacher , Bonn University 19th International Workshop on Weak Interactions and Neutrinos WIN03 Lake Geneva, Wisconsin, Oct. 6th to 11th, 2003 • Discovery Potential in the SM • Investigations of the Higgs Boson Profile • Discovery Potential in the MSSM • MSSM versus SM (a first look) ?? • Invisible Higgs
Higgs Physics at the Large Hadron Collider. Markus Schumacher , Bonn University 19th International Workshop on Weak Interactions and Neutrinos WIN03 Lake Geneva, Wisconsin, Oct. 6th to 11th, 2003. Discovery Potential in the SM - PowerPoint PPT Presentation
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Higgs Physics at the Large Hadron Collider
Markus Schumacher , Bonn University
19th International Workshop on Weak Interactions and Neutrinos
WIN03
Lake Geneva, Wisconsin, Oct. 6th to 11th, 2003
• Discovery Potential in the SM
• Investigations of the Higgs Boson Profile
• Discovery Potential in the MSSM
• MSSM versus SM (a first look) ??
• Invisible Higgs
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin2
Production and Decay of the SM Higgs Boson at LHC
Having available four production mechanisms and observing several decay modes is the key for investigations of the Higgs boson profile
50 100 200 100010-3
10-2
10-1
100
bb cc tt gg WW ZZ
Bra
nching
ratio
(Higgs
)
mH (GeV)
bb WW
ZZ
tt
cc
gg
K>1.7
K~1.2
K~1.1
K~1.3
HDECAY: Djouadi, Spira et al.
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin3
Discovery Potential 2001 + Main Channels
light Higgs boson M<2MZ:gluon fusion GF with: H , H ZZ 4l H WW ll
associated production: tth, Hbb
2001: 10fb-1 from both experiments for discovery of small mass Higgs
New: weak boson fusion WBF qqqqH with H and HWW
heavy Higgs boson M>2MZ
GF: HZZ4l,
WBF: qqqqH with
HZZll
HZZlljj
HWWljj
Require forward jet tagging
Status 2001
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin4
Detectors optimised for low mass Higgs discovery
current LHC schedule: start 2007> 10 fb-1 / yr at low luminosity (few 1033cm-2s-1) runninglater 100 fb-1 /year at high luminosity (1034cm-2s-1) running
pixel vertex and strip track detectors b andtagging (H, bb)
homogenous calorimeters to large e/ measurement (Hgg, H4 leptons) forward jet tagging (VBF), missing energy (HHinvisible)
for VBF channels only int. luminosity of 30 fb-1 assumed
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin21
Parameter Determination: 4 Scenarios
CP-even, Spin=0 (several mass degenerate states fine) measurement of rates
only one Higgs boson measurement of ratios of branching ratios = measurement of ratios of partial decay widths
only dominant SM couplings are present, no extra particles or strong couplings to light fermions measurement of ratios of couplings and lower limit on total width from visible decays
visible decays ~ visible decays in SM measurement of absolute couplings and
total decay width
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin22
CP even Spin 0: Measurement of RatesSimultaneous global likelihood fit of signal rates xBR in all channels to number of selected events
Takes into account: cross talk between channels (e.g. GF events selected in VBF analysis) statistical fluctuations detector effects: uncertainties of lumi measurement ,
efficiencies for tau, b-, forward jet tagging, and electron reconstruction background estimates: sidebands + shape + theoretical prediction uncertainties to signal rate from PDFs and QCD corrections
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin23
1 Higgs Boson: Ratio of Partial Widths
WWHZH,
WWHWH,
WWHttH,
WWHVBF,
WWHGF,
BR)(
BR)(
BR)(
BR)(
BR)(
W
b
WWW
Z
fit parameters:
All rates can be expressed by above parameters
H WW chosen as reference as best measured for MH>120 GeV
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin24
Ratio of Couplings
H
2w
2W
2t
2W
2b
2W
2
2W
2Z g
gg
gg
gg
gg
fit parameters:
2ZZHZH
2WWHWH
2tttHttH
2ZZF
2wWFVBF
2tggHggH
g
g
g
gg
g
Fix scale as H not
measurable
Production cross sections
7%
15%
4%
20%
WH
ttH
ZFWF
ggH
from theory with assumed uncertainty
b loop neglected for now in ggH
assumptions: only SM particles couple to Higgs boson no large couplings of light fermions
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin25
2W
2W
2Z
2W
2W
2t
ggH
ZZHggH,
g
g
gg
g
g
BR)(
H
2b
b
H
2
H
t(t)W(W)
H
2Z
Z
H
2W
W
g bb)BR(H
g )BR(H
gg )BR(H
g ZZ)BR(H
g WW)BR(H
2
Branching ratios
Rate as function of xi, e.g.
=1%
Ratio of Couplings
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin26
Top Quark Yukawa Coupling: effect of b-loop
Effect of b loop: ~5% in SM
For MH<150 GeV b-coupling determined from ttH,Hbb
For larger MH, b coupling only via GF effects top coupling determination
1) Limit b coupling to less that 10 (50) x SM value
2) No b-loop determination only via ttH, HWW
+ t b
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin27
Total Decay Width H
for MH200 GeV, tot>1GeV direct measurement from mass peak in ZZ4 leptonsBelow 200 GeV: indirect split
g
H
2w
g 2W into and
lower limit on H
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin28
Absolute Coupling Measurement + H
detect.)BR(H
detect.)BR(H
SMSM
detect.)BR(HSMSM 1
Assume: sum of visible BRs have SM value
ZZ, WW
ZZ, WW bb
detectable
only detectable
SMSM
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin29
MSSM: Heavy Higgs Bosons H,A,H+-
Neutral: H and A
•Main discovery decay modes: H/A and H/A enhanced with tan
•Production: direct gg->H/A and associated ggbbH/A
MA>300, tan>10: >90% from ass.
H+-and H+-tb for MH>Mt
Charged: H+-
Decay modes:
Production:1) MH<Mt: top pair production with decay tb H+-
2) gbt H+- gg(qq)tb H+- qqH+-
2 to 2 2 to 3
Transistion region around mt
not studied yet (now in HERWIG)
M. Guchait a. S. Moretti, T.Plehn
NLO-MC needed for more sophisticated studies!
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin30
H/A and
good mass resolution ~1% might allow
to disentangle A,H for specific scenarios (e.g. intense coupling scenario)
determine total width of A which may be a few to 10 GeV
require two and 1 or 2 b-tagged jets
M(GEV)
CMS:20fb-1
tan=30M=130 GeV
H/A
CMS 30fb-1
Low mass <~ 400: lep. lep. lep. had.
Large mass >~400: had. had.
larger rate, trigger on hard tau jets
Eff.(LV1TR)= 80% =95% offline selected events
Tau ID: Eff(tau)=55% Rejection(QCD)=2500
Tau ID and missing E resolution crucial
H/A
ATLAS 30fb-1
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin31
Discovery Potential for H and A
CMS L=100 fb-1
e.g. A,H
4 leptons + Emiss
00
isolation + Z veto SM BGveto nr. and energies of jets,limit on EmissSUSY-BG
discovery potential depends on SUSY parameters: BR, M signal and BG
intermediate tanregion not coverable by SM decay modes
consider SUSY decays of H/A or H/A in SUSY decay decades
(proposed e.g. by Djouadi et al.)
signal
BG: SM+SUSY
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin32
Higgs Decays to Gauginos
ATLAS:Scan in mSUGRAM1/2= 100 to 300 GeVM = 50,100,150,200 GeVSign()=+
CMS:
Specific set
M1=60 GeV
M2=120/180 GeV
M=-500GeV
Ml=250GeV
Mq,g=1TeV
300 fb-1
5 contours
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin33
Masses and tan from neutral Higgs bosons
Error on masses
m/m = 0.1 to few %
Error on tan
tan/tan
= 15 to 5 %
from rates of H/A
VBF h/Hnot studied yet ATLAS TDR
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin34
MH<mt: tt, tbH+- ,H+-
Leptonic channel (ATLAS and CMS):
tH+b; H+; hadr. + t bW bl
Look for an excess of leptons over SM predictions
BR (H±) 100 % for mH<mtop
Hadronic channel (ATLAS):
tH+b; H+; hadr. + tbWbqq
Transverse mass ( jet, Emiss) can be used
for mass measurement in likelihood fit:
Mgen=127.0 GeV Mrec=128.4±1.0 (stat) GeV
but error dominated by systematics (~4 GeV)energy scale, background shape,....
t
ATLAS 10 fb-1
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin35
reconstruct had. top decay and taujetuse spin corr. in decay
(spin 1 versus spin 0)
->
L
,a1
TL ,a1L
tt background
Signal
MH>mt: gbtH+- H+-and H+-tb
H+; hadr. t bW bqq
large background (tt+jets)
reconstruct tops and Higgs MH
H+tb t bW blqq
CMS L= 30 fb-1
CMS L= 30 fb-1
determine MT(jet, ETmiss)
P/E(-jet)
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin36
Hadronic channel analysis closes „hole“ at tan~7Further studies
(proposed by Moretti et al)
1) correct handle of
2 to 3 process transition
2) ggtbHtbtbblbqq for high mass region
3) investigate decay modes in SUSY particles
ATLAS, 30fb-1
(1) (3)
(2)
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin37
ATLAS study
tb
From transverse mass in H case.From invariant mass in Htb case.Precision dominated by statistics. Systematics: bg rate and shape,
energy scale.
xBR ~ tan2 for large tan
Precision limited by uncertainties in luminosity and systematics.
Masses and tan from charged Higgs bosons
tan/tanM/M
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin38
Updated MSSM Scan (ATLAS)
Influence mainly phenomenology of light Higgs boson h
1) MHMAX scenario (MSUSY=1 TeV ) maximal theoretically allowed region for mh
2) Nomixing scenario (now MSUSY= 2 TeV, 1TeV almost excluded by LEP )
small mh difficult for LHC
3) Gluophobic scenario (MSUSY=350GeV)
coupling to gluons suppressed (cancellation of top + stop loops)
small rate for gluon gluon H, Hand Z4 leptons
4) Small scenario (MSUSY = 800 GeV) coupling to b (and ) suppressed (cancellation of sbottom, gluino loops) for large tanb and MA 100 to 500 GeV
New calculations for masses and branching ratios (Feynhiggs1.3, Heinemeyer et al., HDECAY3.0, Spira et al.)
New channels added, in particular VBF channels
New benchmark scenarios considered (proposed by Carena et al.)
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin39
VBF, HiggsNo Lose in MSSM
ATLAS: MHMAX scenario
Parton level study by Plehn, Rainwater, Zeppenfeld
Maximal Mixing Scenario ,MSUSY=1TeV
(for Mh/H>100 GeV)
No lose in MSSM with 40 fb-1
ATLAS: (for Mh/H>110 GeV)
h, H
MHMAX Scenario, MSUSY=1TeV
Area not excluded by LEP covered with 30 fb-1
Other benchmark scenarios not yet checked
h
H
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin40
Mass of the light Higgs boson h
130GeV<Mh
120<Mh<130GeV
110<Mh<120GeV
100<Mh<110GeV
90<Mh<100GeV
Mh<90GeV
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin41
Light Higgs boson h: 30 fb -1
bbh
VBF, h
VBF,h+WW
tthbb
WWhlbb
VBF,hWW
VBF channels
cover large part of
MSSM plane
combined
Excluded by LEP
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin42
Light Higgs boson h: 10 fb -1
5 discovery
3observation
5 discovery
3observation
Almost no individual channel observable
need combination of all channels
Excluded by LEP
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin43
Light Higgs boson h: 300 fb-1
All three
only B
A and B
A and C
For high lumi.: A: h B: tthbb C: hZZ4l contribute
Excluded by LEP
bbh
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin44
h: Number of observable final states
1 channel
2 channels
3 channels
4 channels
5 channels
several channels
observable
allows parameter determination
300 fb-1
Excluded by LEP
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin45
How many can be seen: h,H,A,H+- ?
MHMAX scenario 300 fb-1
1 boson
2 bosons
3 bosons
All 4 bosons
h only
h,H,A,H+-
h,H,A
No holes !
Complete plane covered
h,H,A
(also in other 3 benchmark scenarios)
Excluded by LEP
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin46
Only h seen: is it the SM or the MSSM ?
BR(h) BR(hWW)
R =
From VBF (30fb-1)
=(RMSSM-RSM)exp
> 2 >1
First preliminary look
532
>1 Higgs boson
only h
> 1 Higgs boson
MHMAX scenario, 300fb-1
Only statistical error
Excluded by LEP
Future work: apply coupling measurement study to MSSM
How far SM vs MSSM discrimination in „wegde area“ ?
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin47
Invisible Decays of the Higgs
VBF most promising process !!
Trigger on forward jets + missing ET
CMS fine ! (eff.>95%)
ATLAS: cal. trigger only up to 3.2 so far
studies in progress ! going to 4.9 increase
significance by factor 2.5
Selection:
1) VBF cuts: forward jet tagging central jet-veto, Mjj
2) lepton veto, ptmiss
3) jj <1
Background estimate from qqZ(W) with Zll (Wlto level of 3%
Jet
Jet
ATLAS
MH=130GeV
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin48
Sensitivity to Invisible Decays of Higgs
ATLAS: preliminary investigations of tthblnbqq inv. + Zhll inv
Sensitivity lower by 1/3 to 1/6ATLAS
Difference due to survival probability of jet veto
CMS: parametrisations by Zeppenfeld et al.
ATLAS: cuts on PYTHIA MC
Both include 3% uncertainty on background estimation
w/o syst uncertainty sensitivity increased by factor 2
Markus Schumacher, Bonn University Higgs Physics at LHC WIN03 Lake Geneva, Wisconsin49
Conclusions and Outlook
Very good SM and MSSM discovery potential in first years increased significantly by VBF channels light Higgs boson can be observed in several channels
Progress on coupling measurement also driven by VBF channels might be useful for discrimination between SM and MSSM
Sensitivity of LHC for invisible Higgs decays shown
Continue and reinvestigate channel studies with full simulation, NLO calculations, high luminosity scenario (e.g. potential of VBF, mass measurements) need NLC MC (e.e. bbA/H), matching ME to parton shower
Consider new Higgs scenarios MSSM with CP violation, NMSSM, Little Higgs (work started)
Improve and use coupling measurement to discriminate SM Higgs sector from ist extensions