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Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
A/H -> and H+ -> in CMS
R. Kinnunen
Physics at LHC Prague July 6 - 12, 2003
Helsinki Institute of PhysicsHelsinki, Finland
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Contents
H/A -> H/A -> Cross sections and branching fractionsHadronic trigger-jet identification and hadronic jet suppression tagging with impact parameter measurementb-jet tagging in bbH/ASignal to background ratios and expected discovery reaches,tan mesurement from event rates
H+ ->
Cross sections and branching fractionsTrigger for H+ -> in fully hadronic events polarization in H+ -> and W+ -> Signal to background ratios and expected discovery reaches, tan mesurement from event rates
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
- Efficient background reduction with b tagging in bbH/A
Relative to SM, H/A -> ZZ, WW are strongly suppressed but
- Higgs boson mass reconstruction for H,A ->
Hbb, H, H couplings are enhanced at high tan
How to search for heavy neutral MSSM Higgs bosons
use bbH for production with H/A -> decay channels
- 3 final states for H/A -> (jet+jet, lepton+jet, lepton+lepton)
- H/A -> bb may be also viable (under study)
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Production and decay of H, A
Production through gg -> H/A and gg -> bbH/A
gg->bbH/A dominates the production at large tan ~90% of the total production cros section
BR(H -> ) ~ 10% for tan > 10
For large mA, enhancement of BR(H->) for larger || parameter due suppression of H,A -> decays
HIGLU,HQQ from of M. Spira et al.
Pole mass for Yukawa coupling
g
gg
g
H
H
b
b
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Final states investigated for H, A ->
H -> -> 2 jets BR ~ 42.0%
Backgrounds from QCD multijet events, Z,* ->, tt, Wt, W+jetsH, A -> -> lepton + jet BR ~ 45.6%H, A -> ->2 leptons BR ~ 12.4%
Backgrounds from Z,* ->, tt, bb, Wt, WW, W+jets
Simulation tools
PYTHIA for event generationHDECAY for normalization of cross sections and branching fractionsfor two- jet and two-lepton channelsFull simulation for trigger, selection, b tagging, mass reconstructionFast simulation for signal to background ratios
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Hadronic Tau trigger
Level-1 output rate of 1-Tau and 2-Tau triggers: 3 kHz at low luminosity 6 kHz at high luminosityHLT output rate on tape for ’s: 4 (10) Hz at low (high) luminosity
93 (112) GeV for 1-Tau for low (high) luminosity 66 (76) GeV for 2-Tau for low (high) luminosity
Trigger requirements:
Efficiency: 78 (54)% for H->, mH = 200 GeV, 1 or 2 Tau 81 (72)% for H+->, mH+ = 200 GeV, 1 Tau
Level-1 1-Tau and 2-Tau triggers
on the calorimeter jet reconstructed in 12x12 trigger towers with maximum Et
in the central 4x4 towers and no significant activity in the neighbouring towers (trigger tower = HCAL cell + 5x5 ECAL cells, x = 0.087x0.087 in the barrel)
The required Level-1 rate can be achieved with the thresholds of
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Level-2 Tau trigger
Reconstruction of a jet centered at the hardest Level-1 jetIsolation in the EM calorimeter:
Suppression of 3 for QCD background with Et
em < 5.6 GeV
Signal efficiency ~ 85% same for mH = 200 and 500 GeV
Efficiency (QCD vs H->1/3 prong jets)
as a function of Etcut-off
- sum of the Et deposits in ECAL within 0.13 < R(jet direction, cell) < 0.4
jet definition:Etem <
Etcut-off
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Level-3 Pixel Tau trigger
1. Reconstruction of tracks around the Level-1 jet direction
2. Small signal cone (RS = 0.07) around the hardest track3. Larger isolation cone around jet direction
Accept tracks only in the signal cone
HLT efficiency for 1 or 3 tracks in the signal cone and for R = 0.35:
QCD suppression ~ 103
signal efficiency ~ 40%
using track counting in the Pixel (vertexing) detector: - good efficiency required, high pt accuracy not needed
Efficiency (QCD vs H->1/3 prong jets)as a function of the isolation cone size
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Off-line jet identification
Exploits further the narrowness and the isolation of the jet in the full tracker
Define a narrow signal cone r = 0.03 (0.07 for HLT)
around the leading track direction
1. Leading track cut: Find the leading track in the L1 jet, set a cut pt > 40 GeV
jet isolation: No track, pt > 1 GeV, allowed within 0.03 < R < 0.4
3. Number of tracks in the signal cone: 1 or 3 tracks in the signal cone (pt
leading > 40 GeV)
4. Further reduction of hard QCD jets: Very hard QCD jets can be further suppressed with a cut in pt
leading / Etjet
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Simulation of the QCD di-jet background
using (for the moment) a rejection factor as a function of Et
jet (initial QCD di-jet rate ~1012 events for 60 fb-1)
efficiency verified with full simulation and complet reconstruction for pt
gen < 170 GeV
Suppression of ~ 1000 per jetcan be obtained
Signal efficiency (per event) including Level-1 and HLT trigger from full simulation: mH = 200 GeV 0.8%mH = 500 GeV 8.9%
selection efficiency for hadronic QCD jets
from fast simulation
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
impact parameter tagging in H ->
The lifetime is small, c ~ 90 m, but can be still used to further supress the fake ’s from Z -> ll and from QCD multi-jet events using impact parameter measurement (1 or 3 prong ’s) and vertex reconstruction (3 prong ’s)
S. Le
hti
CMS full simulation and reconstruction
Best separation combining the measurementsin the two jets into one variable
sqrt(ip(1)2 + ip()2)
where ip(1) and ip() are significansiesof the impact parameter measurementsof the leading tracks in jets 1 and 2
Signal efficisiency ~ 60%QCD suppression factor of ~ 9
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
B jet tagging in gg -> bbH/ATagging of the associated b jets is the most efficient way to reduce
the Z,* -> (bbZ ~ 1-2 %)and to further reduce the QCD multijet eventsAssociated b jets in gg -> bbH/A are soft and uniformly distributed over || < 2.5:Efficiencies (Et threshold + tagging propability) relatively low
Significance of the signed transverse impact parameterCMS full simulation and complete reconstruction
Tagging algorithm:at least 2 tracks, pt > 1 GeV, ip > 2,inside the jet cone
Efficiency per jet: 32% non- jets in bbH~ 2 % light quark and gluon jets
non- jets in gg -> bbH/A
jets in QCD di-jet events
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Higgs boson mass reconstruction in H ->
The neutrinos from H -> ( -> hadrons+, -> l+) are emitted closeto the directions of the visible ’s (jets or leptons):
neutrino reconstruction possible using the Etmiss
measurement in events with < 180o, efficiency ~ 50 % (for E E >0)
mH = sqrt(2 E E (1-cosjj
Higgs boson mass from full simulation for H -> -> two jets, mH = 500 GeV, tan = 20,with jetjet < 175o
Efficiency (cut E E>0) 36% fit 14.9%
Efficiency and resolution sensitive to the Et
miss measurement and to the cut
jet, e, jet, e,
jet
Etmiss
jj
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Event selection for A,H->-> 2 jets
Basic event selection: - 2 jets passing the Level-1 and HLT triggers and the off-line selection (1 or 3 hard tracks, isolation)- tagging with impact parameters- Higgs boson mass reconstruction ( cut, E, E > 0)
i) Further selection with Etmiss:
- Etmiss > 40 GeV
-central jet veto beyond 30 GeV
ii) Further selection with b-jet tagging:- one b-tagged jet, Et > 20 GeV- central jet veto beyond 30 GeV
Two alternatives for further reduction:
larger staistics but poor S/B much improved S/B but lower statistics
Total background Total
backgroundTotal background
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Leptonic final states, H/A -> -> e, ll Event selection:
- 2 isolated leptons, pt > 20 GeV - one tagged b jet, veto on second central jet beyond 30 GeV
- impact parameter tagging lepton+lepton final states can be used to double the statistics
lepton + jet final states, H/A -> ->l + jetEvent selection: - one isolated lepton (pt > 20 GeV), one jet (Et > 40 GeV) - one tagged b jet, second jet veto - Higgs boson mass reconstruction
Reach not yet optimized for large mA (> 200 GeV) in CMS
H/A -> -> emA = 200 GeVtan = 20
H/A -> -> ll
- Higgs boson mass reconstruction
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Expected 5-discovery reach for H/A ->
Results for H/A -> from full simulation and complete reconstruction
Variation of BR(H -> ) due to H -> ij
decay modes ~ 40% at mH=500 GeV, tan=20,for -200 GeV < < 500 GeV
Higgs boson mass resolution ~ 2%
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Measurement of tan in H -> from event rates
using the tan dependence BR ~ tan2 * x
- Luminosity uncertaintyL/L ~ 5% - Theoretical uncertainty on the cross section for gg -> bbH: dx/x ~ 30%- The gg -> bbH component is selected by b jet tagging: 1b or 2b tagging, less theoretical uncertainty and higher experimental purity with 2b tagging
tan/tan = ½ * sqrt((NS+NB) / NS2 + (L/L)2 + (x/x)2)
tan/tan 1b tagging 2b taggingH/A -> -> 2 jets, mA= 500 GeV, tan = 40, 60 fb-1 16%
19%
H/A -> -> lepton + jets, mA= 200 GeV, tan = 20, 30 fb-1 16%
H/A -> -> e, mA= 140 GeV, tan = 14, 30 fb-1 18%
dominated byrate uncertaintyup to tan ~ 30
Precision of Higgs boson mass measurement in H/A -> -> 2 jets mA= 500 GeV, tan = 40 , 60 fb-1 mH/mH = 1.5%mA= 200 GeV, tan = 40 , 60 fb-1 mH/mH = 1. 2%
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
How to search for charged Higgs bosons at LHC
If mH+ < mtop: Production through tt events, t -> bH+
accessible through the H+ ->t2-> lepton+qq final state If mH+ > mtop: Production through gg -> tbH+, gb -> tH+, qq’ -> H+, gg -> H+H-, gg -> W+H-
-gg -> tbH+, gb -> tH+ most promising processes, cross sections large enough and the associated top and b jets can be used for background reduction
H+
H+
- gg -> H+H-, gg -> W+H- have small production cross sections-Event rate sufficient for qq’ -> H+-> but suppression of the qq’ -> W-> background is difficult
tg
b
g
g
t
b
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
One tagged b jet enough to suppress the backgrounds, use gb -> tH+
Event generation with PYTHIANormalization of the production cross sections toT. Plehn, MADPH-02-1275
T. Plehn
Normalization of branching fractions to HDECAY
HDECAY
tan = 30
H+ ->
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Trigger for H+ -> , -> jet +
-Cut on the leading track and isolation needed
Level-1: single Tau trigger (Et > 93 GeV, low luminosity)
High Level Trigger: cut on Et
miss in the calorimetry (possible due to off-line Etmiss > 100
GeV)
Level-3 Single Tau:
- Reconstruction of tracks in the full tracker within the L1 jet
Efficiency for ptleading track > 20 GeV and
isolation in 0.065 < R < 0.4: QCD rejection ~ 30Signal efficiency ~ 58%
QCD rejection ~ 100 for Etmiss > 65
GeVEfficiency (QCD vs H->1/3 prong jets)as a function of pt cut for the leading track
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
polarization in H+ -> and W+ ->
H+
+
+
+
H+ -> leads to harder pions from and from the longidutinalcomponents of and a1 than the corresponding decays in W+ ->
W+
+
+
+
TAUOLA interfaced to PYTHIA
->L
,a1
TL ,a1
L
Large suppression of W -> in tt, Wt, W+jet using the cut:
pleading track / E jet > 0.8:
Signal, mH+= 400 GeV 46%Signal, mH+= 200 GeV 22%tt background 1.8%
jet = calorimeter jet from -> hadrons +
tt background
Signal
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Event selection for gb -> tH±, H± ->
Quasi two-body decay between the jet and Et
miss in fully hadronic events -> almost background-free situation in mT(-jet,Et
miss)
- Et jet > 80 – 100 GeV, containing a hard track with pt
track/Et jet > 0.8
- Etmiss > 100 GeV
- Veto on 5th jet, veto on second top quark
Cut on ( jet, Etmiss) ->
low mass background can be suppressed
( jet, Etmiss) > 20o
mT( jet, Etmiss)
- Reconstruction of associated hadronic top from two jetand one b-tagged jet
( jet, Etmiss)
tt background
Signal
Signal
Signal
background
background
30 fb-1
30 fb-1
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Expected 5-discovery reach for charged Higgs boson
H+ -> tb and qq’ -> H+ -> are also promising
good background knowledge needed
Excess of ’s can be measured in tt, t -> bH+, H+ -> for mH+ < mtop
No sensitivity for intermediate tan with gb -> tH+ (with SM decay channels):H+ -> Wh, h -> bb accessible (in MSSM) only at small tan
tan measurement from event rates using ~ tan2 at high tanExpected uncertainty for tan >30 with 20% theoretical
uncertainty :tan/tan < 14% for mH+ = 200 GeVtan/tan < 20% for mH+ = 400 GeV
Physics at LHCPrague, 6-12 July, 2003
R. KinnunenHelsinki Institute of Physics
Conclusions
H/A -> accessible for 30 fb-1 with e and ll final states for tan > 14 at mA = 140 GeV jet+ lepton final states for tan > 10 at mA = 200 GeVand for 60 fb-1 with 2 jet final states for tan > 18 at mA = 200 GeV tan > 25 at mA = 500 GeV
tan determination with event rates: tan/tan = 16% for H/A -> -> 2 jets, mA = 500 GeV, tan = 40 16% for H/A -> -> lepton+jet, mA = 200 GeV, tan = 20 18% for H/A -> -> e, mA = 140 GeV, tan = 14 14% for gb -> tH+ ,H+ -> , mA = 200 GeV, tan = 30
H+ -> accessible in gb -> tH+ in fully hadronic final states with 30 fb-
1 for tan > 20 at mA = 200 GeV tan > 32 at mA = 400 GeV
Search for H/A and H+ can start early, with < 10 fb-1
With ~ 60 fb-1 masses in the 500 – 800 GeV range accessible
more specifically:
mH/mH in H/A -> -> 2 jets, tan = 40, 60 fb-1 : 1.2% for mA = 200 GeV 1.5% for mA = 500 GeV
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