121 research outputs found
Transformation properties of the transverse mass under transverse Lorentz boosts at hadron colliders
The transverse mass of semi-invisibly decaying particles, calculated from the
transverse momenta of their decay products, has been used in a broad range of
searches and measurements at hadron colliders, such as the LHC. This variable
is invariant by construction under Lorentz boosts purely in the longitudinal
(beam) direction, thereby minimising sensitivity to fluctuations in the
fractions of the proton momentum carried by the colliding partons. In this
paper we examine, by contrast, the properties of the transverse mass under
boosts with a component also in the transverse plane perpendicular to the beam
direction. We show that this variable is invariant under such boosts in cases
where the boost is purely transverse and (a) the momenta of the decay products
are confined to the transverse plane in the rest frame of the parent particle
and/or (b) the transverse momenta of the decay products are perpendicular to
the boost direction. We discuss the transformation properties of the transverse
mass in the case of combined transverse and longitudinal boosts and identify
the criteria under which the transverse mass in the laboratory frame can equal
the rest mass of the parent particle, irrespective of its value in the rest
frame of the parent.Comment: 7 pages double column, 7 figures, formatted for EPJ
Inclusive SUSY Searches and Measurements at ATLAS
Results of a new study of the discovery potential within mSUGRA parameter space of inclusive searches for SUSY at ATLAS are presented. These results indicate that superior performance is provided by the jets + missing ET channel in which no requirements are placed upon lepton multiplicity. The sensitivity of this and other channels is mapped in m0 - m1/2 parameter space for four different values of tan(beta) with similar performance being obtained in all cases Inclusive measurements of the effective mass scale and total production cross-section of supersymmetric particles are also discussed and results presented of a study of the likely measurement precision
Supersymmetric particle mass measurement with invariant mass correlations
The kinematic end-point technique for measuring the masses of supersymmetric
particles in R-Parity conserving models at hadron colliders is re-examined with
a focus on exploiting additional constraints arising from correlations in
invariant mass observables. The use of such correlations is shown to
potentially resolve the ambiguity in the interpretation of quark+lepton
end-points and enable discrimination between sequential two-body and three-body
lepton-producing decays. The use of these techniques is shown to improve the
SUSY particle mass measurement precision for the SPS1a benchmark model by at
least 20-30% compared to the conventional end-point technique.Comment: 29 pages, 23 .eps figures, JHEP3 style; v2 adds some references and
small clarifications to text; v3 adds some more clarifications to the tex
A hybrid method for determining particle masses at the Large Hadron Collider with fully identified cascade decays
A new technique for improving the precision of measurements of SUSY particle
masses at the LHC is introduced. The technique involves kinematic fitting of
events with two fully identified decay chains. We incorporate both event ETmiss
constraints and independent constraints provided by kinematic end-points in
experiment invariant mass distributions of SUSY decay products. Incorporation
of the event specific information maximises the information used in the fit and
is shown to reduce the mass measurement uncertainites by ~30% compared to
conventional fitting of experiment end-point constraints for the SPS1a
benchmark model.Comment: 10 pages, 2 .eps figures, JHEP3 styl
Transverse mass and invariant mass observables for measuring the mass of a semi-invisibly decaying heavy particle
Formulae are derived for the positions of end-points in the invariant mass
and transverse mass distributions obtained from the products of heavy states
decaying to pairs of semi-invisibly decaying lighter states. Formulae are
derived both for the special case where the two decay chains are identical and
the more general case where they are different. The formulae are tested with a
simple case study of heavy SUSY higgs particles decaying to gauginos at the
LHC.Comment: 13 pages, 8 eps figure
Supersymmetric particle mass measurement with the boost-corrected contransverse mass
A modification to the contransverse mass (MCT) technique for measuring the
masses of pair-produced semi-invisibly decaying heavy particles is proposed in
which MCT is corrected for non-zero boosts of the centre-of-momentum (CoM)
frame of the heavy states in the laboratory transverse plane. Lack of knowledge
of the mass of the CoM frame prevents exact correction for this boost, however
it is shown that a conservative correction can nevertheless be derived which
always generates an MCT value which is less than or equal to the true value of
MCT in the CoM frame. The new technique is demonstrated with case studies of
mass measurement with fully leptonic ttbar events and with SUSY events
possessing a similar final state.Comment: 33 pages, 33 .eps figures, JHEP3 styl
Vorinostat: A Potent Agent to Prevent and Treat Laser-Induced Corneal Haze
PURPOSE—This study investigated the efficacy and safety of vorinostat, a deacetylase (HDAC) inhibitor, in the treatment of laser-induced corneal haze following photorefractive keratectomy (PRK) in rabbits in vivo and transforming growth factor beta 1 (TGFβ1) -induced corneal fibrosis in vitro.
METHODS—Corneal haze in rabbits was produced with −9.00 diopters (D) PRK. Fibrosis in cultured human and rabbit corneal fibroblasts was activated with TGFβ1. Vorinostat (25 μm) was topically applied once for 5 minutes on rabbit cornea immediately after PRK for in vivo studies. Vorinostat (0 to 25 μm) was given to human/rabbit corneal fibroblasts for 5 minutes or 48 hours for in vitro studies. Slit-lamp microscopy, TUNEL assay, and trypan blue were used to determined vorinostat toxicity, whereas real-time polymerase chain reaction, immunocytochemistry, and immunoblotting were used to measure its efficacy.
RESULTS—Single 5-minute vorinostat (25 μm) topical application on the cornea following PRK significantly reduced corneal haze (Pin vivoscreened 4 weeks after PRK. Vorinostat reduced TGFβ1-induced fibrosis in human and rabbit corneas in vitro in a dose-dependent manner without altering cellular viability, phenotype, or proliferation.
CONCLUSIONS—Vorinostat is non-cytotoxic and safe for the eye and has potential to prevent laser-induced corneal haze in patients undergoing PRK for high myopia
Constraining Dark Matter in the MSSM 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 SPA benchmark model based on measurements
of end-points and thresholds in the invariant mass spectra of various
combinations of leptons and jets. These measurements are used to constrain the
soft SUSY breaking parameters at the electroweak scale in a general MSSM model.
Based on these constraints, we assess the accuracy with which the Dark Matter
relic density can be measured.Comment: 21 pages, 12 figure
Status of ZEPLIN II and ZEPLIN IV study
Abstract We discribe the construction status of ZEPLIN II detector, a 30-kg two-phase discriminating xenon detector to be installed in Boulby Mine, UK, for the direct detection of WIMP dark matter. Both scintillation and ionization will be measure in order to discriminate the radioactive background. ZEPLIN-II will have very high radioactive-background rejection efficiency. We will also discuss the study of ton scale ZEPLIN IV. The ZEPLIN program is a collaborative work of UCLA, TAMU, UKMDMC, and CNR Torino, Italy
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