472 research outputs found
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
Comparison of ground and aerial application of fungicide for control of Ascochyta blight in chickpeas
Non-Peer ReviewedAscochyta rabiei control from aerial and ground application was assessed near Saskatoon in 2003 and 2004. Each year, a site of about 12 ha was seeded to kabuli (cv. CDC Xena) chickpeas. At the first sign of disease, applications of fungicide were commenced and maintained at approximately 10-day intervals. In 2003, four applications (two with Headline (pyraclostrobin), two with Lance (boscalid)) were conducted. In 2004, the last Lance application was not done. Aerial application was made using a Cessna AgTruck applying 37 L/ha using CP nozzles emitting a spray with a VMD of approximately 271 μm. Ground applications were conducted using a Melroe SpraCoupe applying 100 L/ha using XR8003 nozzles with a VMD of approximately 246 μm. Disease ratings were done throughout the season, and seed yields were
taken at crop maturity. Disease incidence progressed to 80 to 90% in the untreated plots, and fungicide application reduced disease incidence (to 20 to 30%) and increased seed yield in both years. Disease incidence and seed yield were not affected by application method in either season
Renormalization group parameter evolution of the minimal supersymmetric standard model with R-parity violation
A comparison of spectra obtained using the 1-loop MSSM and 2-loop R-parity
violating MSSM renormalization group equations is presented. Influence of
higher loop corrections and R-parity violating terms is discussed. Some
numerical constraints on the R-parity violating parameters are also given.Comment: 4 pages, 1 figure, using RevTE
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
Using Subsystem MT2 for Complete Mass Determinations in Decay Chains with Missing Energy at Hadron Colliders
We propose to use the MT2 concept to measure the masses of all particles in
SUSY-like events with two unobservable, identical particles. To this end we
generalize the usual notion of MT2 and define a new MT2(n,p,c) variable, which
can be applied to various subsystem topologies, as well as the full event
topology. We derive analytic formulas for its endpoint MT2{max}(n,p,c) as a
function of the unknown test mass Mc of the final particle in the subchain and
the transverse momentum pT due to radiation from the initial state. We show
that the endpoint functions MT2{max}(n,p,c)(Mc,pT) may exhibit three different
types of kinks and discuss the origin of each type. We prove that the subsystem
MT2(n,p,c) variables by themselves already yield a sufficient number of
measurements for a complete determination of the mass spectrum (including the
overall mass scale). As an illustration, we consider the simple case of a decay
chain with up to three heavy particles, X2 -> X1 -> X0, which is rather
problematic for all other mass measurement methods. We propose three different
MT2-based methods, each of which allows a complete determination of the masses
of particles X0, X1 and X2. The first method only uses MT2(n,p,c) endpoint
measurements at a single fixed value of the test mass Mc. In the second method
the unknown mass spectrum is fitted to one or more endpoint functions
MT2{max}(n,p,c)(Mc,pT) exhibiting a kink. The third method is hybrid, combining
MT2 endpoints with measurements of kinematic edges in invariant mass
distributions. As a practical application of our methods, we show that the
dilepton W+W- and tt-bar samples at the Tevatron can be used for an independent
determination of the masses of the top quark, the W boson and the neutrino,
without any prior assumptions.Comment: 47 pages, 9 figures. revised version, published in JHEP. Major
addition: a new appendix with the complete set of formulas for the MT2
endpoints as functions of the upstream transverse momentum pT and test mass
M
Naturalness Priors and Fits to the Constrained Minimal Supersymmetric Standard Model
We examine the effect of a prior that favours low values of fine-tuning on
Bayesian multi-dimensional fits of the constrained minimal supersymmetric
standard model (CMSSM or mSUGRA) to current data. The dark matter relic
density, the anomalous magnetic moment of the muon and the branching ratio of
b->s gamma are all used to constrain the model via a Markov Chain Monte Carlo
sampler. As a result of the naturalness prior, posterior probability
distributions skew towards lighter higgs and sparticle masses, the effect being
most pronounced in the gaugino sector. Interestingly, slepton masses are an
exception and skew towards heavier masses. The lightest CP-even Higgs h^0-pole
region becomes allowed at the 2 sigma level for the latest combination of
measurements of m_t=172.7+/-2.9 GeV, provided we allow for a theoretical error
in the prediction of its mass m_{h^0}. m_{h^0} is constrained to be less than
120 GeV at the 95% C.L. Probing the branching ratio of B_s->mu^+ mu^- to the
level of 2 x 10^{-8}, as might be achieved by the Tevatron experiments, would
cover 32% of the probability density, irrespective of which of the two priors
is used.Comment: 15 pages, 5 figures. Ref adde
Sparticle Spectra and LHC Signatures for Large Volume String Compactifications
We study the supersymmetric particle spectra and LHC collider observables for
the large-volume string models with a fundamental scale of 10^{11} GeV that
arise in moduli-fixed string compactifications with branes and fluxes. The
presence of magnetic fluxes on the brane world volume, required for chirality,
perturb the soft terms away from those previously computed in the dilute-flux
limit. We use the difference in high-scale gauge couplings to estimate the
magnitude of this perturbation and study the potential effects of the magnetic
fluxes by generating many random spectra with the soft terms perturbed around
the dilute flux limit. Even with a 40% variation in the high-scale soft terms
the low-energy spectra take a clear and predictive form. The resulting spectra
are broadly similar to those arising on the SPS1a slope, but more degenerate.
In their minimal version the models predict the ratios of gaugino masses to be
M_1 : M_2 : M_3=(1.5 - 2) : 2 : 6, different to both mSUGRA and mirage
mediation. Among the scalars, the squarks tend to be lighter and the sleptons
heavier than for comparable mSUGRA models. We generate 10 fb^{-1} of sample LHC
data for the random spectra in order to study the range of collider
phenomenology that can occur. We perform a detailed mass reconstruction on one
example large-volume string model spectrum. 100 fb^{-1} of integrated
luminosity is sufficient to discriminate the model from mSUGRA and aspects of
the sparticle spectrum can be accurately reconstructed.Comment: 42 pages, 21 figures. Added references and discussion for section 3.
Slight changes in the tex
Discriminating Electroweak-ino Parameter Ordering at the LHC and Its Impact on LFV Studies
Current limit on the dark matter relic abundance may suggest that
should be smaller than prediction in the minimal supergravity scenario (mSUGRA)
for moderate and . The electroweak-ino parameter and
are then much closer to each other. This can be realized naturally in
the non-universal Higgs mass model (NUHM). Since the heaviest neutralino
() and chargino () have significant gaugino
components, they may appear frequently in the left-handed squark decay and then
be detectable at the LHC. In such a case, we showed that the hierarchy of and can be determined. In the light slepton mass scenario with
non-vanishing lepton-flavor violation (LFV) in the right-handed sector, NUHM
with small corresponds to region of parameter space where strong
cancellation among leading contributions to can occur. We
showed that determination of electroweak-ino hierarchy plays a crucial role in
resolving cancellation point of and determination of LFV
parameters. We also discussed test of the universality of the slepton masses at
the LHC and the implications to SUSY flavor models.Comment: 34 pages, 16 figure
Measuring superparticle masses at hadron collider using the transverse mass kink
We present a detailed study of the collider observable applied for
pair-produced superparticles decaying to visible particles and a pair of
invisible lightest supersymmetric particles (LSPs). Analytic expressions of the
maximum of over all events () are derived. It is
noticed that if the decay product of each superparticle involves more than one
visible particles, being a function of the {\it trial} LSP
mass has a kink structure at true LSP mass, which can be
used to determine the mother superparticle mass and the LSP mass
simultaneously. To see how well can be constructed from
collider data, a Monte-Carlo analysis of the gluino is performed for
some superparticle spectra.Comment: Typos corrected. A few references added. Figures update
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