Report on the Activities of

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Report on the Activities of WORKING GROUP
I Collider Physics
Coordinators Sunanda Banerjee Rohini M.
Godbole Sreerup Raychaudhuri
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• Working Group Talks
• Gobinda Majumdar
• Issues In The Construction Of Detectors
  For ILC
• Satyaki Bhattacharyya
• Photon Detection Efficiency In The
  Measurement
• Of
• Ben Allanach
• Dark Matter Constraints on the Parameter space
  of the MSSM and mSUGRA

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D E F I N E D P R O B L E M S

1. Z-boson decay to a photon graviton
2. Light charged Higgs in the NMSSM with and without
   CP-violation
3. SUSY Studies at LHC in the light of Dark Matter
   Constraints
4. Observing the Higgs through its decay into a tau
   and a muon
5. CP-violating observables in Higgs decays at the
   LHC
6. Benchmark points for little Higgs models with
   T-parity

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1.
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2.
Light charged Higgs in the NMSSM with without
CP-violation D.P.Roy, D.Choudhury, R.Godbole,
D.Miller, S.P.Das, S.Kraml, S.K.Rai

• LEP Bound of 114 GeV forces the MSSM
  pseudoscalar to be
• heavy and hence the charged Higgs to be heavier
  than the top quark

• Can be relaxed in
• NMSSM
• CP-violating MSSM

• Possible to have a light pseudoscalar and a
  light charged Higgs
• of mass 120 160 GeV in the
  regime

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• at LHC

• Final state is 2j 4b
• Reconstruction of t gets rid of QCD backgrounds
• Channel is shown to work

PROPOSAL Carefully study region in NMSSM
parameter space where this scenario dominates,
e.g. vacuum stability. Extend for NMSSM with
CP-violation.
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SUSY dark matterB. Allanach, SP Das, RM Godbole,
M Guchait, S Kraml, D P Roy
3.

• In stau coannihilation scenario, stau-LSP mass
  difference is 10 GeV or smaller
• New feature in LHC cascade decays
• soft taus
• Need to investigate whether soft tau signal can
  be dectected at LHC

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• SPS3 inspired scenario
• m080, m1/2400, A00, tb10, sgn(m)
• Not most favorable point but ok to start with

neutralino1 158 GeV stable
stau1 168 GeV 100 to LSP
tau-sneutrino 275 GeV 87 to LSP 12 to Wstau
neutralino2 304 GeV 16 stautau 16 sleptonlepton
chargino1 304 Gev 19 stauneutrino 20 sneutrinotau
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pt of ts from neutralino2 chain

• Taus from neutralino2 decay into stautau are no
  problem ptmean147 GeV
• Taus from stau decay into LSP are very soft
  ptmean19 GeV
• Very unlikely to get mtt endpoint.
• Add. info from mll or nt2?nt1h may help to
  contrain stau mass

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pt of ts from chargino1 chain
chargino1?stauneutrino?tauneutrinoLSP

• Tau is again soft
• ptmax,mean 26 GeV
• Rapidity distribution within the tracker range

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Stop coannihlation

• Stop-LSP mass difference 20-30 GeV.
• Gluino will decay into stoptop
• 50 same-sign top quarks ? same-sign leptons due
  to Majorana nature of gluino hep-ph/0512284
• Intend more detailed study for coannihilation
  region cLSP as well as 3/4-body stop decay
  modes.

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Summary of Problem 3

• Stau coannihilation scenario
• stau-LSP mass difference
• 10 GeV or smaller
• new feature in LHC cascade
• decays soft taus
• Study how signal can be extracted
• Stop coannihilation scenario
• stop-LSP mass difference 20-30 GeV
• Gluino will decay into stoptop 50 same-sign
  top quarks
• ? same-sign leptons because gluino is Majorana
  hep-ph/0512284
• More detailed study in small DM region, incl
  cLSP and 3-body
• stop decay modes

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4.
Detection of Higgs through its tau-muon decay
D. Zeppenfeld, R. Vaidya, M.Guchait, S.D.
Rindani, D.Miller
No details are available, but it was reported
that it does not seem to be feasible to detect
the Higgs boson through this decay channel.
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CP Observables
5.
Coordinators D. Miller D. Choudhury
Aim To find Higgs sector observables at the LHC
which are zero in models where CP is conserved
but may be non-zero if CP is violated.
Production and decay

• Scalar nature of the Higgs ) there can be no
  correlations between production and decay.
• e.g.
• Need at least 3 directions to construct CP odd
  observable
• e.g. (need
  not be particle momenta may also be
  polarization vectors)

no correlation
These requirements severely limit the possible
channels at the LHC
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MSSM

• Most general HVV vertex contains
• CP-even terms (i.e. )
• CP-odd terms (i.e.
  )
• However, in the MSSM, these CP-odd terms are
  absent at all orders!

In principle, observables like
are CP-violating
observables, but we cannot distinguish the two
gluons in the experiment, so this is no use.
We can here use rapidity to distinguish between
the quark and anti-quark, but this is presumably
too small to be any use (?)
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So we really need a process which doesnt use the
initial state gluons or quarks but still has
plenty of other particles in the production !
associated production
A possible asymmetry is
As a first step, we could just look at
Santosh has agreed to look into this using
MADGRAPH
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More General Models
In principle, other models of new physics could
contain AVV couplings, with a coefficient
suppressed by MEW/?. What is the sensitivity of
the LHC to such couplings? (Are there already
constraints from LEP?) Look at Higgs decays via
Possible Asymmetry David Miller, Margarete
Mühlleitner Rohini Godbole have agreed to look
at this. Note that this is the crossing of the
process
which Rohini et al have already looked at
for CP-violating observables.
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Little Higgs Model with T Parity
6.
M.Perelstein, S.K.Rai, R. Godbole, S.Kraml,
N.Okada

• Little Higgs models are viable theories of EWSB
  with a composite Higgs
• LH with T Parity (a la R parity of the MSSM)
  passes electroweak precision tests without
  fine-tuning
• New T-odd states an extra set of SU(2)xU(1)
  gauge bosons, partners of (left-handed) quarks
  and leptons, a triplet Higgs field

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LHT _at_ LHC Phenomenology

• Predominant production channel _at_ the LHC
  pair-production of heavy quarks Q'
• Lightest T-odd Particle (LTP) is stable
  typically the heavy photon B' -gt missing energy
  signal
• Look for cascade decays Q' -gt (jets, leptons)B'
• This is just like the MSSM!

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LHT or SUSY?

• How can the LHC experiments distinguish between
  these models? Non-trivial -gt interesting!
• First step identify benchmark points in LHT and
  SUSY with the same observable particle spectra
  for a fair comparison
• LHT spectrum is not entirely flexible -gt cannot
  be faked by the usual mSUGRA

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LHT/SUSY Comparison Benchmark Point(s)

• In SUSY we need gaugino mass non-universality
  M2/M14 at the weak scale
• We found a good benchmark point with this
  property by deforming the SPS1a.
• Substantial rate of dilepton cascade decays at
  this point will allow for a precise determination
  of the spectrum at the LHC
• A more general scan of SUSY parameter space could
  also be useful

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LHT/SUSY Comparison Plan

• The next step is to compute event rates and
  distributions at the benchmark point and look for
  good discriminating signatures
• This will require simulation tools for the LHT
  model implement this model in existing event
  generators?

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Concluding Remarks

• We have identified 5 problems which seem
  interesting and worth pursuing
• Preliminary discussions have clarified the
  problems and indicated a plan of action for each
• A contact person has been identified for each
  problem and he/she will be requested to provide a
  more detailed write-up for the WG report
• All that remains is to do the work!