5,934 research outputs found
LHC Signature of Mirage Mediation
We study LHC phenomenology of mirage mediation scenario in which anomaly and
modulus contributions to soft SUSY breaking terms are comparable to each other.
A Monte Carlo study of mirage mediation, with model parameters , GeV, , and , is presented. It is
shown that masses of supersymmetric particles can be measured in a model
independent way, providing information on SUSY breaking sector. In particular,
the mass ratio of gluino to the lightest neutralino for the benchmark scenario
is determined to be 1.9 \lesssim m_{\tildeg}/m_{\tilde\chi_1^0} \lesssim 3.1,
well reproducing theoretical input value of which is quite distinctive from the predictions of other SUSY scenarios in which gaugino
masses are unified at the GUT scale. The model parameters of mirage mediation
can be also determined from various kinematic distributions
Signals from R-parity violating top quark decays at LHC
We evaluate the potential of the CERN LHC collider to observe rare decays of
the top quark in channels involving R-parity violating (RPV) interactions. We
stress the importance of calculating top quark production and decay
simultaneously as a true 2->4 process.
The process of tt-bar pair production followed by RPV decay of one of the top
quarks is analyzed with fast detector simulation. We show that intermediate
supersymmetric particles can be observed as resonances even if they are heavier
than the top quark due to the significant off-shell top-quark mass effects. The
approach where the top quark is produced on-mass-shell and then decays into 2-
or 3-body final state would in general lead to incorrect kinematical
distributions and rates. The rates of the 2 -> 4 process with top quark
production and RPV 3-body decay depend on the total width of the heavy
intermediate sfermion which could,therefore, be measured indirectly.
We find that the LHC collider offers a unique potential to study rare top
quark decays in the framework of supersymmetry with broken R-parity for
branching fractions of RPV top decays as low as 10^{-6}Comment: 23 pages, 22 figure
Pair production of charged Higgs scalars from electroweak gauge boson fusion
We compute the contribution to charged Higgs boson pair production at the
Large Hadron Collider (LHC) due to the scattering of two electroweak (EW) gauge
bosons, these being in turn generated via bremsstrahlung off incoming quarks: q
q --> q q V^*V^* --> q q H^+H^- (V=gamma,Z,W^{+/-}). We verify that the
production cross section of this mode is tan beta independent and show that it
is smaller than that of H^+H^- production via q q-initiated processes but
generally larger than that of the loop-induced channel gg --> H^+H^-. Pair
production of charged Higgs bosons is crucial in order to test EW symmetry
breaking scenarios beyond the Standard Model (SM). We show that the detection
of these kind of processes at the standard LHC is however problematic, because
of their poor production rates and the large backgrounds.Comment: 22 pages, latex, 8 figures (largely revised version to appear in JPG
Constraining SUSY Dark Matter with the ATLAS Detector at the LHC
In the event that R-Parity conserving supersymmetry (SUSY) is discovered at
the LHC, a key issue which will need to be addressed will be the consistency of
that signal with astrophysical and non-accelerator constraints on SUSY Dark
Matter. This issue is studied for the SPS1a mSUGRA benchmark model by using
measurements of end-points and thresholds in the invariant mass spectra of
various combinations of leptons and jets in ATLAS to constrain the model
parameters. These constraints are then used to assess the statistical accuracy
with which quantities such as the Dark Matter relic density and direct
detection cross-section can be measured. Systematic effects arising from the
use of different mSUGRA RGE codes are also estimated. Results indicate that for
SPS1a a statistical(systematic) precision on the relic abundance ~ 2.8% (3 %)
can be obtained given 300 fb-1 of data.Comment: 11 pages, 10 encapsulated postscript figures. Minor modification to
ref
Dark matter searches at LHC
Besides Standard Model measurements and other Beyond Standard Model studies,
the ATLAS and CMS experiments at the LHC will search for Supersymmetry, one of
the most attractive explanation for dark matter. The SUSY discovery potential
with early data is presented here together with some first results obtained
with 2010 collision data at 7 TeV. Emphasis is placed on measurements and
parameter determination that can be performed to disentangle the possible SUSY
models and SUSY look-alike and the interpretation of a possible positive
supersymmetric signal as an explanation of dark matter.Comment: 15 pages, 14 figures, Invited plenary talk given at DISCRETE 2010:
Symposium On Prospects In The Physics Of Discrete Symmetries, 6-11 Dec 2010,
Rome, Ital
A mobile data acquisition system
A mobile data aquisition (MobiDAQ) was developed for the ATLAS central hadronic
calorimeter (TileCal). MobiDAQ has been designed in order to test the functionalities of the TileCal
front-end electronics and to acquire calibration data before the final back-end electronics were built
and tested. MobiDAQ was also used to record the first cosmic ray events acquired by an ATLAS
subdetector in the underground experimental area
Probing RS scenarios of flavour at LHC via leptonic channels
We study a purely leptonic signature of the Randall-Sundrum scenario with
Standard Model fields in the bulk at LHC: the contribution from the exchange of
Kaluza-Klein (KK) excitations of gauge bosons to the clear Drell-Yan reaction.
We show that this contribution is detectable (even with the low luminosities of
the LHC initial regime) for KK masses around the TeV scale and for sufficiently
large lepton couplings to KK gauge bosons. Such large couplings can be
compatible with ElectroWeak precision data on the Zff coupling in the framework
of the custodial O(3) symmetry recently proposed, for specific configurations
of lepton localizations (along the extra dimension). These configurations can
simultaneously reproduce the correct lepton masses, while generating acceptably
small Flavour Changing Neutral Current (FCNC) effects. This LHC
phenomenological analysis is realistic in the sense that it is based on fermion
localizations which reproduce all the quark/lepton masses plus mixing angles
and respect FCNC constraints in both the hadron and lepton sectors.Comment: 15 pages, 6 Figures, Latex fil
Possible Single Resonant Production of the Fourth Generation Charged Leptons at Colliders
Single resonant productions of the fourth standard model generation charged
lepton via anomalous interactions at gamma e colliders based on future linear
e^+ e^- colliders with 500 GeV and 1 TeV center of mass energies are studied.
Signatures of and
anomalous processes followed by the hadronic and leptonic decay of the Z boson
and corresponding standard model backgrounds are discussed in details. The
lowest necessary luminosities to observe these processes and the achievable
values of the anomalous coupling strengths are determined.Comment: 9 pages, 6 figures, 4 table
Forward production of beauty baryons in pp collisions at LHC
The production of charmed and beauty baryons in proton-proton collisions at
high energies is analyzed within the modified quark-gluon string model. We
present some predictions for the experiments on the forward beauty baryon
production in pp collisions at LHC energies. This analysis allows us to find
useful information on the Regge trajectories of the heavy (b barb) mesons and
the sea beauty quark distributions in the proton.Comment: 14 pages, 12 figure
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