57,781 research outputs found
Neutralino Warm Dark Matter
In the supersymmetric (SUSY) standard model, the lightest neutralino may be
the lightest SUSY particle (LSP), and it is is a candidate of the dark matter
in the universe. The LSP dark matter might be produced by the non-thermal
process such as heavy particle decay after decoupling of the thermal relic LSP.
If the produced LSP is relativistic, and does not scatter enough in the thermal
bath, the neutralino LSP may contribute as the warm dark matter (WDM) to wash
out the small scale structure of O(0.1) Mpc. In this letter we calculate the
energy reduction of the neutralino LSP in the thermal bath and study whether
the LSP can be the WDM. If temperature of the production time T_I is smaller
than 5MeV, the bino-like LSP can be the WDM and may contribute to the
small-scale structure of O(0.1) Mpc. The Higgsino-like LSP might also work as
the WDM if T_I< 2MeV. The wino-like LSP cannot be the WDM in the favoured
parameter region.Comment: 13 pages. Some references are added in revised versio
Cartel Duration and Endogenous Private Monitoring and Communication: An Instrumental Variables Approach
Colluding firms often exchange private information and make transfers within the cartels based on the information. Estimating the impact of such collusive practicesâ known as the âlysine strategy profile (LSP)ââ on cartel duration is difficult because of endogeneity and omitted variable bias. I use firmsâ linguistic differences as an instrumental variable for the LSP in 135 cartels discovered by the European Commission since 1980. The incidence of the LSP is not significantly related to cartel duration. After correction for selectivity in the decision to use the LSP, statistical tests are consistent with a theoretic prediction that the LSP increases cartel duration
All Possible Lightest Supersymmetric Particles in R-Parity Violating mSUGRA Models and their Signals at the LHC
We consider minimal supergravity (mSUGRA) models with an additional R-parity
violating operator at the grand unification scale. This can change the
supersymmetric spectrum leading on the one hand to a sneutrino, smuon or squark
as the lightest supersymmetric particle (LSP). On the other hand, a wide
parameter region is reopened, where the scalar tau is the LSP. It is vital to
know the nature of the LSP, because supersymmetric particles normally cascade
decay down to the LSP at collider experiments. We investigate in detail the
conditions leading to non-neutralino LSP scenarios. We also present some
typical LHC signatures.Comment: 4 pages, 4 figures, submitted for the proceedings of the SUSY09
conferenc
Long-Lived Unstable Superparticles at the LHC
In various models of supersymmetry (SUSY), the lightest superparticle in the
minimal SUSY standard model sector, which we call MSSM-LSP, becomes unstable.
Then, we may observe the decay of the MSSM-LSP in the detector at the LHC
experiment. We show that the discovery of such a decay process (and the
determination of the lifetime of the MSSM-LSP) may be possible at the LHC even
if the decay length of the MSSM-LSP is much longer than the size of the
detector; sizable number of the MSSM-LSPs decay inside the detector if the
lifetime is shorter than 0.01-1 millisec. We also discuss the implications of
the study of the MSSM-LSP decay for several well-motivated SUSY models.Comment: 13 pages, 4 figure
Spin-dependent constraints on blind spots for thermal singlino-higgsino dark matter with(out) light singlets
The LUX experiment has recently set very strong constraints on
spin-independent interactions of WIMP with nuclei. These null results can be
accommodated in NMSSM provided that the effective spin-independent coupling of
the LSP to nucleons is suppressed. We investigate thermal relic abundance of
singlino-higgsino LSP in these so-called spin-independent blind spots and
derive current constraints and prospects for direct detection of spin-dependent
interactions of the LSP with nuclei providing strong constraints on parameter
space. We show that if the Higgs boson is the only light scalar the new LUX
constraints set a lower bound on the LSP mass of about 300 GeV except for a
small range around the half of boson masses where resonant annihilation
via exchange dominates. XENON1T will probe entire range of LSP masses
except for a tiny -resonant region that may be tested by the LZ
experiment. These conclusions apply to general singlet-doublet dark matter
annihilating dominantly to . Presence of light singlet
(pseudo)scalars generically relaxes the constraints because new LSP (resonant
and non-resonant) annihilation channels become important. Even away from
resonant regions, the lower limit on the LSP mass from LUX is relaxed to about
250 GeV while XENON1T may not be sensitive to the LSP masses above about 400
GeV.Comment: 31 pages, 8 figure
Phenomenology of a Long-Lived LSP with R-Parity Violation
We present the leading experimental constraints on supersymmetric models with
R-parity violation (RPV) and a long-lived lightest superpartner (LSP). We
consider both the well-motivated dynamical RPV scenario as well as the
conventional holomorphic RPV operators. Guided by naturalness, we study the
cases of stop, gluino, and higgsino LSPs with several possible leading decay
channels in each case. The CMS displaced dijet and the ATLAS multitrack
displaced vertex searches have been fully recast, with all cuts and vertex
reconstruction algorithms applied. Heavy charged stable particle searches by
CMS are also applied. In addition, we consider representative bounds for prompt
LSP decays that are directly applicable. Our main results are exclusion plots
in the plane for the various scenarios. We find
that the natural parameter space ( GeV,
GeV, GeV) is excluded for a long-lived
LSP ( mm).Comment: 25 pages, 8 figure
Ultra-high energy LSP
We argue that the lightest supersymmetric particles (LSP) can be produced
with extremely high energies E\gsim 10^{10} GeV in the Universe at the
present epoch. Their most probable sources are decaying superheavy particles
produced by topological defects or as relic Big Bang particle. We discuss the
mechanisms of production of LSP at ultra-high energies (UHE) and the
interaction of the UHE LSP with matter. The most attention is given to the
neutralino as LSP, although the gluino is also considered as a phenomenological
possibility.Comment: 14 pages, 4 ps figures, Latex2
Right-handed sneutrino dark matter and big-bang nucleosynthesis
We study the light-element abundances in supersymmetric model where the
right-handed sneutrino is the lightest superparticle (LSP), assuming that the
neutrino masses are purely Dirac-type. In such a scenario, the lightest
superparticle in the minimal supersymmetric standard model sector (which we
call MSSM-LSP) becomes long-lived, and thermal relic MSSM-LSP may decay after
the big-bang nucleosynthesis starts. We calculate the light-element abundances
including non-standard nuclear reactions induced by the MSSM-LSP decay, and
derive constraints on the scenario of right-handed sneutrino LSP.Comment: 13 pages, 4 figure
Splitting along a submanifold pair
The paper introduces a group of obstructions for splitting a homotopy
equivalence along a pair of submanifolds. We develop exact sequences relating
the -groups with various surgery obstruction groups for manifold triple
and structure sets arising from triples of manifolds. The natural map from the
surgery obstruction group of the ambient manifold to the -group provides
an invariant when elements of the Wall group are not realized by normal maps of
closed manifolds. Some -groups are computed precisely.Comment: K-theory, to appea
Impact of LSP Character on Slepton Reach at the LHC
Searches for supersymmetry at the Large Hadron Collider (LHC) have
significantly constrained the parameter space associated with colored
superpartners, whereas the constraints on color-singlet superpartners are
considerably less severe. In this study, we investigate the dependence of
slepton decay branching fractions on the nature of the lightest supersymmetric
particle (LSP). In particular, in the Higgsino-like LSP scenarios, both decay
branching fractions of and depend strongly on
the sign and value of , which has strong implications for the reach of
dilepton plus MET searches for slepton pair production. We extend the
experimental results for same flavor, opposite sign dilepton plus MET searches
at the 8 TeV LHC to various LSP scenarios. We find that the LHC bounds on
sleptons are strongly enhanced for a non-Bino-like LSP: the 95% C.L. limit for
extends from 300 GeV for a Bino-like LSP to about 370 GeV
for a Wino-like LSP. The bound for with a Higgsino-like LSP is
the strongest (~ 490 GeV) for ~ and is the weakest
(~ 220 GeV) for ~ . We also calculate prospective
slepton search reaches at the 14 TeV LHC. With 100 fb integrated
luminosity, the projected 95% C.L. mass reach for the left-handed slepton
varies from 550 (670) GeV for a Bino-like (Wino-like) LSP to 900 (390) GeV for
a Higgsino-like LSP under the most optimistic (pessimistic) scenario. The reach
for the right-handed slepton is about 440 GeV. The corresponding 5
discovery sensitivity is about 100 GeV smaller. For 300 fb integrated
luminosity, the reach is about 50 - 100 GeV higher.Comment: 24 pages, 10 figure
- âŠ