Download Working Group Talks Gobinda Majumdar Issues In The Construction

Report on the Activities of
WORKING GROUP I
Collider Physics
Coordinators:
Sunanda Banerjee
Rohini M. Godbole
Sreerup Raychaudhuri
Working Group Talks
• Gobinda Majumdar
Issues In The Construction Of Detectors For ILC
• Satyaki Bhattacharyya
Photon Detection Efficiency In The Measurement
Of H 0  
• Ben Allanach
Dark Matter Constraints on the Parameter space of
the MSSM and mSUGRA
DEFINED
PROBLEMS
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
1.
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
M 2  M A2  M W2
• 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 tan   5 regime
• at LHC
t

t


bW
bH +  hW
BR ~1%

bb
• 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.
3.
SUSY dark matter
B. Allanach, SP Das, RM Godbole, M Guchait, S Kraml, D P Roy
• 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
• SPS3 inspired scenario:
m0=80, m1/2=400, A0=0, t=10, sgn(m)=+
neutralino1
158 GeV
stable
stau1
168 GeV
100% to LSP
tausneutrino
275 GeV
87% to LSP
12% to W+stau
neutralino2 304 GeV 16% stau+tau
16% slepton+lepton
chargino1
304 Gev 19% stau+neutrino
20% sneutrino+tau
Not most favorable point but ok to start with
pt of t´s from neutralino2 chain
• Taus from neutralino2
decay into stau+tau are
no problem; ptmean=147
GeV
• Taus from stau decay into
LSP are very soft;
ptmean=19 GeV
• Very unlikely to get mtt
endpoint.
• Add. info from mll or
nt2→nt1+h may help to
contrain stau mass
pt of t´s from chargino1 chain
chargino1→stau+neutrino→tau+neutrino+LSP
• Tau is again soft;
ptmax,mean = 26 GeV
• Rapidity distribution within
the tracker range
Stop coannihlation
• Stop-LSP mass difference ~20-30 GeV.
• Gluino will decay into stop+top;
50% same-sign top quarks → same-sign leptons
due to Majorana nature of gluino [hep-ph/0512284]
• Intend more detailed study for coannihilation
region; c+LSP as well as 3/4-body stop decay
modes.
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 stop+top; 50% same-sign top quarks
→ same-sign leptons because gluino is Majorana [hep-ph/0512284]
– More detailed study in small DM region, incl c+LSP and 3-body
stop decay modes
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.
5.
CP Observables
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.
no correlation
Need at least 3 directions to construct CP odd observable
e.g.
(need not be particle momenta – may also be polarization vectors)
These requirements severely limit the possible channels at the LHC
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!
must rely on
vertices
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 (?)
So we really need a process which doesn’t 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
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
Rohini et al have already looked at for CP-violating observables.
which
6.
Little Higgs Model with T Parity
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
LHT @ LHC: Phenomenology
• Predominant production channel @ the
LHC: pair-production of heavy quarks Q'
• Lightest T-odd Particle (LTP) is stable;
typically the “heavy photon” B' -> missing
energy signal
• Look for cascade decays: Q' -> (jets,
leptons)+B'
• This is just like
the MSSM!
LHT or SUSY?
• How can the LHC experiments distinguish
between these models? Non-trivial ->
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 ->
cannot be faked by the usual mSUGRA
LHT/SUSY Comparison:
Benchmark Point(s)
• In SUSY we need gaugino mass nonuniversality: M2/M1~4 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
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?
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!