5,039 research outputs found
Decoding the Mechanism for the Origin of Dark Matter in the Early Universe Using LHC Data
It is shown that LHC data can allow one to decode the mechanism by which dark
matter is generated in the early universe in supersymmetric theories. We focus
on two of the major mechanisms for such generation of dark matter which are
known to be the Stau Coannihilation (Stau-Co) where the neutralino is typically
Bino like and annihilation on the Hyperbolic Branch (HB) where the neutralino
has a significant Higgsino component. An investigation of how one may
discriminate between the Stau-Co region and the HB region using LHC data is
given for the mSUGRA model. The analysis utilizes several signatures including
multi leptons, hadronic jets, b-tagging, and missing transverse momentum. A
study of the SUSY signatures reveals several correlated smoking gun signals
allowing a clear discrimination between the Stau-Co and the HB regions where
dark matter in the early universe can originate.Comment: 7 pages, 5 figs, 2 columns, Accepted for publication in Physical
Review
Inclusive SUSY Searches using Missing Energy plus Multijets in pp collisions at =14 TeV with CMS
An inclusive analysis strategy for SUSY searches in pp collisions at sqrt(s)=14 TeV with the CMS detector is discussed. The missing transverse energy plus multijets canonical signature is used. Emphasis is put in methods to normalize the backgrounds using the data and in understanding the experimental systematic uncertainties. A 5 sigma excess can be observed with O(pb^-1) at a particular low mass SUSY point. The 5 sigma discovery reach contours in the mSUGRA parameter space for 1 and 10 fb^-1 are obtained
Using Jet Substructure at the LHC to Search for the Light Higgs Bosons of the CP-Violating MSSM
The CP-violating version of the Minimal Supersymmetric Standard Model (MSSM)
is an example of a model where experimental data do not preclude the presence
of light Higgs bosons in the range around 10 -- 110 GeV. Such light Higgs
bosons, decaying almost wholly to b-bbar pairs, may be copiously produced at
the LHC, but would remain inaccessible to conventional Higgs searches because
of intractable QCD backgrounds. We demonstrate that a significant number of
these light Higgs bosons would be boosted strongly enough for the pair of
daughter -jet pairs to appear as a single `fat' jet with substructure.
Tagging such jets could extend the discovery potential at the LHC into the
hitherto-inaccessible region for light Higgs bosons.Comment: LaTeX, 33 pages, 5 eps figures and 5 tables embedded. minor changes,
to appear in Physical Review
Commissioning of the CMS zero degree calorimeter using LHC beam
This paper reports on the commissioning and first running experience of the
CMS Zero Degree Calorimeters during December 2009. All channels worked
correctly. The ZDCs were timed into the data acquisition system using beam
splash events. These data also allowed us to make a first estimate of
channel-by-channel variations in gain.Comment: 6 pages, 8 figures, Presented at CALOR2010: 14th International
Conference for Calorimetry in High Energy Physic
Where the Sidewalk Ends: Jets and Missing Energy Search Strategies for the 7 TeV LHC
This work explores the potential reach of the 7 TeV LHC to new colored states
in the context of simplified models and addresses the issue of which search
regions are necessary to cover an extensive set of event topologies and
kinematic regimes. This article demonstrates that if searches are designed to
focus on specific regions of phase space, then new physics may be missed if it
lies in unexpected corners. Simple multiregion search strategies can be
designed to cover all of kinematic possibilities. A set of benchmark models are
created that cover the qualitatively different signatures and a benchmark
multiregion search strategy is presented that covers these models.Comment: 30 pages, 8 Figures, 3 Tables. Version accepted at JHEP. Minor
changes. Added figur
Exact Solution of Photon Equation in Stationary G\"{o}del-type and G\"{o}del Space-Times
In this work the photon equation (massless Duffin-Kemmer-Petiau equation) is
written expilicitly for general type of stationary G\"{o}del space-times and is
solved exactly for G\"{o}del-type and G\"{o}del space-times. Harmonic
oscillator behaviour of the solutions is discussed and energy spectrum of
photon is obtained.Comment: 9 pages,RevTeX, no figure, revised for publicatio
Bigger, Better, Faster, More at the LHC
Multijet plus missing energy searches provide universal coverage for theories
that have new colored particles that decay into a dark matter candidate and
jets. These signals appear at the LHC further out on the missing energy tail
than two-to-two scattering indicates. The simplicity of the searches at the LHC
contrasts sharply with the Tevatron where more elaborate searches are necessary
to separate signal from background. The searches presented in this article
effectively distinguish signal from background for any theory where the LSP is
a daughter or granddaughter of the pair-produced colored parent particle
without ever having to consider missing energies less than 400 GeV.Comment: 26 pages, 8 Figures. Minor textual changes, typos fixed and
references adde
Decay mechanisms in CdS buffered Cu In,Ga Se2 thin film solar cells after exposure to thermal stress Understanding the role of Na
Due to their tunable bandgap energy, Cu In,Ga Se2 CIGSe thin film solar cells are an attractive option for use as bottom devices in tandem configurations. In monolithic tandem devices, the thermal stability of the bottom device is paramount for reliable application. Ideally, it will permit the processing of a top device at the required optimum process temperature. Here, we investigate the degradation behavior of chemical bath deposited CBD CdS buffered CIGSe thin film solar cells with and without Na incorporation under thermal stress in ambient air and vacuum with the aim to gain a more detailed understanding of their degradation mechanisms. For the devices studied, we observe severe degradation after annealing at 300 C independent of the atmosphere. The electrical and compositional properties of the samples before and after a defined application of thermal stress are studied. In good agreement with literature reports, we find pronounced Cd diffusion into the CIGS absorber layer. In addition, for Na containing samples, the observed degradation can be mainly explained by the formation of Na induced acceptor states in the TCO front contact and a back contact barrier formation due to the out diffusion of Na. Supported by numerical device simulation using SCAPS 1D, various possible degradation models are discussed and correlated with our finding
Functional MRI at 1.5 tesla: A comparison of the blood oxygenation level-dependent signal and electrophysiology
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