424 research outputs found
Determining masses of supersymmetric particles
If supersymmetric particles are produced at the Large Hadron Collider it
becomes very important not only to identify them, but also to determine their
masses with the highest possible precision, since this may lead to an
understanding of the SUSY-breaking mechanism and the physics at some higher
scale. We here report on studies of how such mass measurements are obtained,
and how the precision can be optimized.Comment: 11 pages, contribution to the proceedings "II. Southeastern European
Workshop Challenges Beyond The Standard Model", 19-23 May 2005, Vrnjacka
Banja, Serbi
Resolving ambiguities in mass determinations at future colliders
The measurements of kinematical endpoints, in cascade decays of
supersymmetric particles, in principle allow for a determination of the masses
of the unstable particles. However, in this procedure ambiguities often arise.
We here illustrate how such ambiguities arise. They can be resolved by a
precise determination of the LSP mass, provided by the Linear Collider.Comment: 6 pages, 6 figures, to appear in the proceedings of the 2005
International Linear Collider Workshop, Stanford, U.S.
Mass Determination in Cascade Decays Using Shape Formulas
In SUSY scenarios with invisible LSP, sparticle masses can be determined from
fits to the endpoints of invariant mass distributions. Here we discuss possible
improvements by using the shapes of the distributions. Positive results are
found for multiple-minima situations and for mass regions where the endpoints
do not contain sufficient information to obtain the masses.Comment: to appear in Proceedings of SUSY06, the 14th International Conference
on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine,
California, 12-17 June 200
Mass ambiguities in cascade decays
We review the use of invariant mass distributions in cascade decays to
measure the masses of New Physics (NP) particles in scenarios where the final
NP cascade particle is invisible. We extend earlier work by exploring further
the problem of multiple solutions for the masses.Comment: 4 pages, 4 figures, to appear in the proceedings of the XXXIII
International Conference on High Energy Physics (ICHEP'06), July 26 - August
2 2006, Mosco
Spin and model identification of Z' bosons at the LHC
Heavy resonances appearing in the clean Drell-Yan channel may be the first
new physics to be observed at the proton-proton CERN LHC. If a new resonance is
discovered at the LHC as a peak in the dilepton invariant mass distribution,
the characterization of its spin and couplings will proceed via measuring
production rates and angular distributions of the decay products. We discuss
the discrimination of the spin-1 of Z' representative models (Z'_{SSM},
Z'_{psi}, Z'_{eta}, Z'_{chi}, Z'_{LR}, and Z'_{ALR}) against the
Randall-Sundrum graviton resonance (spin-2) and a spin-0 resonance (sneutrino)
with the same mass and producing the same number of events under the observed
peak. To assess the range of the Z' mass where the spin determination can be
performed to a given confidence level, we focus on the angular distributions of
the Drell-Yan leptons, in particular we use as a basic observable an
angular-integrated center-edge asymmetry, A_{CE}. The spin of a heavy Z' gauge
boson can be established with A_{CE} up to M_{Z'} \simeq 3.0 TeV, for an
integrated luminosity of 100 fb^{-1}, or minimal number of events around 110.
We also examine the distinguishability of the considered Z' models from one
another, once the spin-1 has been established, using the total dilepton
production cross section. With some assumption, one might be able to
distinguish among these Z' models at 95% C.L. up to M_{Z'} \simeq 2.1 TeV.Comment: 18 pages, 6 figure
Sneutrino identification in dilepton events at the LHC
Heavy neutral resonances appearing in the clean Drell-Yan channel may be the
first new physics to be observed at the proton-proton CERN LHC. If a new
resonance is discovered at the LHC as a (narrow) peak in the dilepton invariant
mass distribution, the characterization of its spin and couplings will proceed
via the measurement of production rates and angular distributions of the decay
products. We discuss the discrimination of a spin-0 resonance (sneutrino)
predicted by supersymmetric theories with R-parity breaking against the spin-1
of Z^\prime bosons and the Randall-Sundrum graviton resonance (spin-2) with the
same mass and producing the same number of events under the observed peak. To
assess the region of sneutrino parameters (couplings and masses) where the spin
determination can be performed to a given confidence level, we focus on the
event rate and the angular distributions of the Drell-Yan leptons, in
particular using the center-edge asymmetry, A_{\rm CE}. We find that although
the measured event rate permits solving the above problem partially, the
center-edge asymmetry, on the contrary allows to differentiate the various
spins entirely with a minimal number of events around 200.Comment: 20 pages; version to appear in PR
Describing Inequalities in Access to Employment and the Associated Geography of Wellbeing
This paper addresses three questions. How unequal is access to urban employment and the wellbeing associated with it? What is the monetary value consumers place on access? How does the inequality of access correspond to the geographical pattern of unemployment? A novel approach is developed using the Osland and Pryce house price model to estimate the monetary value of access welfare (MVAW)—the wellbeing associated with living a given distance from employment, taking into account the negative externalities associated with centres of employment and the complexities that arise from the existence of multiple employment centres of varying size. It is found that: MVAW is considerably more unequal than house prices or income; MVAW contributes around 13 per cent of the average value of a house; and the spatial pattern of unemployment rates is highly inelastic with respect to both MVAW and employment, suggesting no evidence of a spatial mismatch
Spin identification of the Randall-Sundrum resonance in lepton-pair production at the LHC
The determination of the spin of the quantum states exchanged in the various
non-standard interactions is a relevant aspect in the identification of the
corresponding scenarios. We discuss the identification reach at LHC on the
spin-2 of the lowest-lying Randall-Sundrum resonance, predicted by gravity with
one warped extra dimension, against spin-1 and spin-0 non-standard exchanges
with the same mass and producing the same number of events in the cross
section. We focus on the angular distributions of leptons produced in the
Drell-Yan process at the LHC, in particular we use as basic observable a
normalized integrated angular asymmetry A_{CE}. Our finding is that the 95%
C.L. identification reach on the spin-2 of the RS resonance (equivalently, the
exclusion reach on both the spin-1 and spin-0 hypotheses for the peak) is up to
a resonance mass scale of the order of 1.0 or 1.6 TeV in the case of weak
coupling between graviton excitations and SM particles (k/{\bar M}_{Pl}=0.01)
and 2.4 or 3.2 TeV for larger coupling constant (k/{\bar M}_{Pl}=0.1) for a
time-integrated LHC luminosity of 10 or 100 fb^{-1}, respectively. Also, some
comments are given on the complementary r\^oles of the angular analysis and the
eventual discovery of the predicted second graviton excitation in the
identification of the RS scenario.Comment: 27 pages, 11 figures. v2: References added, clarifications; version
to appear in PR
Signals of additional Z boson in e+e-\to W+W^- at the ILC with polarized beams
We consider the possibility of fingerprinting the presence of heavy
additional Z' bosons that arise naturally in extensions of the standard model
such as E_6 models and left-right symmetric models, through their mixing with
the standard model Z boson. By considering a class of observables including
total cross sections, energy distributions and angular distributions of decay
leptons we find significant deviation from the standard model predictions for
these quantities with right-handed electrons and left-handed positrons at
\sqrt{s}=800 GeV. The deviations being less pronounced at smaller centre of
mass energies as the models are already tightly constrained. Our work suggests
that the ILC should have a strong beam polarization physics program
particularly with these configurations. On the other hand, a forward backward
asymmetry and lepton fraction in the backward direction are more sensitive to
new physics with realistic polarization due to interesting interplay with the
neutrino t- channel diagram. This process complements the study of fermion pair
production processes that have been considered for discrimination between these
models.Comment: 23 pages, 9 figures, uses plain latex; substantially improved
discussion, references added, version accepted for publication in JHE
Spin Discrimination in Three-Body Decays
The identification of the correct model for physics beyond the Standard Model
requires the determination of the spin of new particles. We investigate to
which extent the spin of a new particle can be identified in scenarios
where it decays dominantly in three-body decays . Here we
assume that is a candidate for dark matter and escapes direct detection at
a high energy collider such as the LHC. We show that in the case that all
intermediate particles are heavy, one can get information on the spins of
and at the LHC by exploiting the invariant mass distribution of the two
standard model fermions. We develop a model-independent strategy to determine
the spins without prior knowledge of the unknown couplings and test it in a
series of Monte Carlo studies.Comment: 31+1 pages, 4 figures, 8 tables, JHEP.cls include
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