6,985 research outputs found
Searching for the Kaluza-Klein Graviton in Bulk RS Models
The best-studied version of the RS1 model has all the Standard Model
particles confined to the TeV brane. However, recent variants have the Standard
Model fermions and gauge bosons located in the bulk five-dimensional spacetime.
We study the potential reach of the LHC in searching for the lightest KK
partner of the graviton in the most promising such models in which the
right-handed top is localized very near the TeV brane and the light fermions
are localized near the Planck brane. We consider both detection and the
establishment of the spin-2 nature of the resonance should it be found.Comment: 17 pages, 6 figures - JHEP published version, figures added,
branching ratio correcte
The outlook for precipitation measurements from space
To provide useful precipitation measurements from space, two requirements must be met: adequate spatial and temporal sampling of the storm and sufficient accuracy in the estimate of precipitation intensity. Although presently no single instrument or method completely satisfies both requirements, the visible/IR, microwave radiometer and radar methods can be used in a complementary manner. Visible/IR instruments provide good temporal sampling and rain area depiction, but recourse must be made to microwave measurements for quantitative rainfall estimates. The inadequacy of microwave radiometer measurements over land suggests, in turn, the use of radar. Several recently developed attenuating-wavelength radar methods are discussed in terms of their accuracy, dynamic range and system implementation. Traditionally, the requirements of high resolution and adequate dynamic range led to fairly costly and complex radar systems. Some simplications and cost reduction can be made; however, by using K-band wavelengths which have the advantages of greater sensitivity at the low rain rates and higher resolution capabilities. Several recently proposed methods of this kind are reviewed in terms of accuracy and system implementation. Finally, an adaptive-pointing multi-sensor instrument is described that would exploit certain advantages of the IR, radiometric and radar methods
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
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
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
Predicting Tropical Cyclogenesis with a Global Mesoscale Model: Hierarchical Multiscale Interactions During the Formation of Tropical Cyclone Nargis(2008)
Very severe cyclonic storm Nargis devastated Burma (Myanmar) in May 2008, caused tremendous damage and numerous fatalities, and became one of the 10 deadliest tropical cyclones (TCs) of all time. To increase the warning time in order to save lives and reduce economic damage, it is important to extend the lead time in the prediction of TCs like Nargis. As recent advances in high-resolution global models and supercomputing technology have shown the potential for improving TC track and intensity forecasts, the ability of a global mesoscale model to predict TC genesis in the Indian Ocean is examined in this study with the aim of improving simulations of TC climate. High-resolution global simulations with real data show that the initial formation and intensity variations of TC Nargis can be realistically predicted up to 5 days in advance. Preliminary analysis suggests that improved representations of the following environmental conditions and their hierarchical multiscale interactions were the key to achieving this lead time: (1) a westerly wind burst and equatorial trough, (2) an enhanced monsoon circulation with a zero wind shear line, (3) good upper-level outflow with anti-cyclonic wind shear between 200 and 850 hPa, and (4) low-level moisture convergence
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
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
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
- …