how to exploit t polarization in charged higgs boson searches
DESCRIPTION
How to Exploit t Polarization in Charged Higgs Boson Searches. Prospects for Charged Higgs Discovery at Colliders Uppsala, 13-16 September 2006. R. Kinnunen Helsinki Institute of Physics. Background for t polarization studies. - PowerPoint PPT PresentationTRANSCRIPT
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
How to Exploit Polarization in Charged Higgs Boson Searches
R. KinnunenHelsinki Institute of Physics
Prospects for Charged Higgs Discovery at CollidersUppsala, 13-16 September 2006Uppsala, 13-16 September 2006
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
A method to use polarization to enhance the signal for thecharged Higgs bosons in the H± -> decay channel (in tt and gb->tH± production) was first proposed by DP. Roy, Phys. Lett. B459 (1999) 607.
- The method was applied by the CMS and ATLAS collaborationsin several studies on charged Higgs bosons:R. Kinnunen, CMS Note 2000/045; K.A. Assamagan and Y. Coadou, Acta Phys. Polon. B33 (2002)707; M. Baarmand, M. Hashemi and A. Nikitenko, CMS Note 2006/056; R. Kinnunen, CMS Note 2006/100 (only some examples mentioned)
Background for polarization studies
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
H± -> decay dominates for mH+ < mtop and is large also for mH+ > mtop at large tan
H± and decay modes
Hadronic decay modesBR±±12.5%BR± ±± 026%
BR± a1±± 007.5%
1-prong decay modes ~ 50%3-prong decay modes ~15%
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Background suppression in the charged Higgs bosons searches with the H± -> decays channel
The search channels with H± -> are a subject of background fromgenuine ’s and from hadronic jets faking ’s
Hadronic jets faking jets from QCD multi-jet events, from W/Z+jet and tt events can be suppressed with the hadronic decay properties;narrow jet in calorimeters and 1 or 3 charged particles in the tracker
Mass reconstruction of , track impact parameter measurements andsecondary vertex reconstruction can be used to improve this selection
The backgrounds with genuine ’s from tt and W+3jet backgrounds with W->can be also efficiently suppressed due to the opposite helicity correlations in the H± -> and W± -> decays
The basic event selection requirements, like large ET for the liketrigger jet, already exploit the polarizationSelection can be enhanced with special selection cuts
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Helicity correlations
Center of mass angular distributions of into a meson or a vector meson (,a1) in terms of polarization
L and T are the longitudinal and transverse polarization states of the vector meson. In the laboratory frame
p,V / p =
Harder jet for signal with P = +1 than for the background with P = -1 from the L and a1L contributions, and the opposite from the T and a1T
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Illustration with simple spin arguments for formH+ -> and W+ -> :
HH++
WW++
Helicity correlations
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Energy charing in the vector meson decays
Energy fraction carried by the charged pion in the vector meson decays: ±
L,T -> ±0 and a±1L,T -> ±0 0
from D.P. Roy, Phys. Lett. B459 (1999) 607
For ±L and a±
1L: E± ~ 0 or E± ~ Ea1
for ±T and a±
1T: E± ~ E0
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Exploiting helicity correlations in 1-prong decays
Example of helicity correlations in 1-prong decays in the gb->tH±, H± -> signal and in the tt background with fast simulation and calorimeter smearing
A hard cut, R1 = p / p > 0.8 suppresses efficietly the background from tt, W->
ET jet > 100 GeV
ET jet > 100 GeV
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Helicity correlations in full simulationHelicity correlations in full simulation
Full selection efficiency: signal 11-15%, tt->bbl 5%, W+3jets 1%
Search for light charged Higgs bosons with mH+ < mtop
in gg -> tt -> W±H±bb->lbb, l = e or
one jet with off-line identification: - ET > 40 GeV- tracker and ECAL isolation- 1 or 3 prongs in the signal cone- pleading track/E jet > 0.8
pleading track/E jet forETjet
> 40 GeVandpleading track > 20 GeV
All hadronic decays channels included
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
identification:
Trigger cuts: ETjet
> 93 GeV (Level-1), pTleading track > 25 GeV(HLT)
Main cuts for the off-line selection:- ET
jet > 100 GeV
- 1 or 3 tracks in a small signal cone of R = 0.04- isolation of the signal cone in 0.04<R<0.4- pleading track/Et jet > 0.8
Search for heavy charged Higgs bosons with mH+ > mtop
in gg -> tbH±, H± ->
Helicity correlations in full simulationHelicity correlations in full simulation
All hadronic decays channels included
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Distributions affected by the trigger selection Distributions affected by the trigger selection
-selection efficiencies including pre-selection, trigger and off-line
mmH± (GeV) (GeV) 200 400 tt Wt W+3j QCD
Total efficiency 3.8% 9.0% 5.0x10-4 6.7x10-4 1.9x10-3 9.2x109.2x10-5-5
Signal and background distributions for pleading track/E jet
Large suppression of backgrounds with genuine ’s
±
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Exploiting helicity correlations in 3-prong decays
1) M. Guchait, R. Kinnunen, D.P. Roy, hep-ph/0608324.
The 1-prong selection with pleading track/Et jet > 0.8 suppresses the 3-prong decays from 15% to 3% in the full simulation of thegg -> tbH±, H± -> channel
New idea1) of exploiting more efficiently the 3-prong decaysbased on the decay mode without any accompanying 0’s:
-> ±±±2/3rd the 3-prong decays (10% of total)
This mode can be selected with matching of tracker momentum andcalorimeter signals or by a veto on accompanying in ECAL
The a1L contribution can be enhanced with a cut in the momentumfraction carried by the like-sign pair R3 < 0.4 or R3 > 0.8, R3 = p±±/p-jet
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
R3 = p±±/p-jet distributions for -> 3± with ET jet > 100 GeV
Study for the gb -> tH±, H± -> channel Event generation with PYTHIA, decays with TAUOLA Background from tt events Fast simulation of CMS detector, jet and missing ET reconstruction No trigger simulation
Exploiting helicity correlations in 3-prong decays
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
”Standard” selection used for 1-prong decays only
Exploiting helicity correlations in 3-prong decays
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
New selection for 3-prong decays
Exploiting helicity correlations in 3-prong decays
Selection of->±±±withE = |Etrktot - Ecal
tot|<10 GeV ~ calorimeter resolution
For R3 < 0.4 the event is triggered at HLT with the 3th opposite sign (hard) pion
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
30 fb-1
100 fb-1
Discovery potential with 3-prong selection
Effect of trigger simulation estimated to increase the discovery limits in tan with 25%
gb -> tH±, H± ->
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Prospects of Cherged Higgs Discovery at Colliders, Uppsala,13-16 September 2006, Uppsala,13-16 September 2006
R. KinnunenHelsinki Institute of Physics
Conclusions
Oppositehelicity correlations in the H± -> and W± -> decays allow suppression of the backgrounds with genuine ’s from tt andW+3jet events to a low level with the requirementpleading track/p jet > 0.8 in the 1-prong decays
The discovery reach can be enlarged by ~ 18-12% in tan witha 3-prong selection demanding the like-sign pion pair to carrymore than 80% or less than 40% of the jet momentum