509 research outputs found
CP violation in chargino decays in the MSSM
In the minimal supersymmetric standard model (MSSM) with complex parameters,
supersymmetric loop effects can lead to \emph{CP} violation. We calculate the
rate asymmetries of decays of charginos into the lightest neutralino and a
boson on the basis of the most important loop contributions in the third
generation squark sectors. It turns out that the \emph{CP} violating
asymmetries can be a few per cent in typical regions of the parameter space of
the MSSM. These processes would provide very promising channels for probing
\emph{CP} violation in the MSSM at future high-energy colliders.Comment: 15 pages, 5 figures, LaTeX2
Features of heavy physics in the CMB power spectrum
The computation of the primordial power spectrum in multi-field inflation
models requires us to correctly account for all relevant interactions between
adiabatic and non-adiabatic modes around and after horizon crossing. One
specific complication arises from derivative interactions induced by the
curvilinear trajectory of the inflaton in a multi-dimensional field space. In
this work we compute the power spectrum in general multi-field models and show
that certain inflaton trajectories may lead to observationally significant
imprints of `heavy' physics in the primordial power spectrum if the inflaton
trajectory turns, that is, traverses a bend, sufficiently fast (without
interrupting slow roll), even in cases where the normal modes have masses
approaching the cutoff of our theory. We emphasise that turning is defined with
respect to the geodesics of the sigma model metric, irrespective of whether
this is canonical or non-trivial. The imprints generically take the form of
damped superimposed oscillations on the power spectrum. In the particular case
of two-field models, if one of the fields is sufficiently massive compared to
the scale of inflation, we are able to compute an effective low energy theory
for the adiabatic mode encapsulating certain relevant operators of the full
multi-field dynamics. As expected, a particular characteristic of this
effective theory is a modified speed of sound for the adiabatic mode which is a
functional of the background inflaton trajectory and the turns traversed during
inflation. Hence in addition, we expect non-Gaussian signatures directly
related to the features imprinted in the power spectrum.Comment: 41 pages, 6 figures, references updated, minor modifications. Version
to appear in JCAP. v4: Equations (4.28) and (4.30) and Figures 5 and 6
correcte
Neutralino properties in the light of a further indication of an annual modulation effect in WIMP direct search
We demonstrate that the further indication of a possible annual modulation
effect, singled out by the DAMA/NaI experiment for WIMP direct detection, is
widely compatible with an interpretation in terms of a relic neutralino as the
major component of dark matter in the Universe. We discuss the supersymmetric
features of this neutralino in the Minimal Supersymmetric extension of the
Standard Model (MSSM) and their implications for searches at accelerators.Comment: 15 pages, ReVTeX, 9 figures (included as PS files
Gaugino Mass Nonuniversality and Dark Matter in SUGRA, Strings and D Brane Models
The effects of nonuniversality of gaugino masses on dark matter are examined
within supersymmetric grand unification, and in string and D brane models with
R parity invariance. In SU(5) unified models nonuniversality in the gaugino
sector can be generated via the gauge kinetic energy function which may depend
on the 24, 75 and 200 dimensional Higgs representations. We also consider
string models which allow for nonuniversality of gaugino masses and D brane
models where nonuniversality arises from embeddings of the Standard Model gauge
group on five branes and nine branes. It is found that with gaugino mass
nonuniversality the range of the LSP mass can be extended much beyond the range
allowed in the universal SUGRA case, up to about 600 GeV even without
coannihilation effects in some regions of the parameter space. The effects of
coannihilation are not considered and inclusion of these effects may further
increase the allowed neutralino mass range. Similarly with the inclusion of
gaugino mass nonuniversality, the neutralino-proton () cross-section
can increase by as much as a factor of 10 in some of regions of the parameter
space. An analysis of the uncertainties in the quark density content of the
nucleon is given and their effects on cross-section are discussed.
The predictions of our analysis including nonuniversality is compared with the
current limits from dark matter detectors and implications for future dark
matter searches are discussed.Comment: Revised version, 23 pages, Latex, and 7 figure
Study of J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar
The branching ratios and Angular distributions for J/psi decays to Lambda
Lambdabar and Sigma0 Sigma0bar are measured using BESII 58 million J/psi.Comment: 11 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
Measurement of branching fractions for the inclusive Cabibbo-favored ~K*0(892) and Cabibbo-suppressed K*0(892) decays of neutral and charged D mesons
The branching fractions for the inclusive Cabibbo-favored ~K*0 and
Cabibbo-suppressed K*0 decays of D mesons are measured based on a data sample
of 33 pb-1 collected at and around the center-of-mass energy of 3.773 GeV with
the BES-II detector at the BEPC collider. The branching fractions for the
decays D+(0) -> ~K*0(892)X and D0 -> K*0(892)X are determined to be BF(D0 ->
\~K*0X) = (8.7 +/- 4.0 +/- 1.2)%, BF(D+ -> ~K*0X) = (23.2 +/- 4.5 +/- 3.0)% and
BF(D0 -> K*0X) = (2.8 +/- 1.2 +/- 0.4)%. An upper limit on the branching
fraction at 90% C.L. for the decay D+ -> K*0(892)X is set to be BF(D+ -> K*0X)
< 6.6%
Study of
New data are presented on from a sample of 58M
events in the upgraded BES II detector at the BEPC. There is a
conspicuous signal for and a peak at higher mass which
may be fitted with . From a combined analysis with
data, the branching ratio
is at the 95%
confidence level.Comment: 11 pages, 5 figures. Submitted to Phys. Lett.
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