57 research outputs found
Graviton production with 2 jets at the LHC in large extra dimensions
We study Kaluza-Klein (KK) graviton production in the large extra dimensions
model via 2 jets plus missing transverse momentum signatures at the LHC. We
make predictions for both the signal and the dominant Zjj and Wjj backgrounds,
where we introduce missing P_T-dependent jet selection cuts that ensure the
smallness of the 2-jet rate over the 1-jet rate. With the same jet selection
cuts, the distributions of the two jets and their correlation with the missing
transverse momentum provide additional evidence for the production of an
invisible massive object.Comment: 8 pages, 10 figures, 1 table; Version to be printed in JHE
Xi and AntiXi production in Pb+Pb collisions at 40 AGeV at CERN SPS
First results on the production of Xi and AntiXi hyperons in Pb+Pb
interactions at 40 AGeV are presented. The AntiXi/Xi ratio at midrapidity is
studied as a function of collision centrality. The ratio shows no significant
centrality dependence within statistical errors; it ranges from 0.07 to 0.15.
The AntiXi/Xi ratio for central Pb+Pb collisions increases strongly with the
collision energy.Comment: 6 pages, 6 figures, proceedings of SQM03, to be published in Journal
of Physics G; V2: changes in table 1 and figure
Lepton Polarization Asymmetry in B\to\ell^{+}\ell^{-} decay Beyond the Standard Model
The lepton polarization asymmetry in the B\to\ell^{+}\ell^{-} decay, when one
of the leptons is polarized, is investigated using the most general form of the
effective Hamiltonian. The sensitivity of the asymmetry to the new Wilson
coefficients is studied.Moreover, correlations between the lepton polarization
asymmetry and the branching ratio is studied. It is observed that, there are
not exist such regions of new Wilson coefficients, which the value of branching
ratio coincides with SM result while the lepton polarization does not, i.e new
physics effects can be established by studying lepton polarization only.Comment: 9 pages,4 figure
Leptonic CP violation: zero, maximal or between the two extremes
Discovery of the CP-violation in the lepton sector is one of the challenges
of the particle physics. We search for possible principles, symmetries and
phenomenological relations that can lead to particular values of the
CP-violating Dirac phase, . In this connection we discuss two extreme
cases: the zero phase, , and the maximal CP-violation, , and relate them to the peculiar pattern of the neutrino mixing. The
maximal CP-violation can be related to the reflection
symmetry. We study various aspects of this symmetry and introduce a generalized
reflection symmetry that can lead to an arbitrary phase that depends on the
parameter of the symmetry transformation. The generalized reflection symmetry
predicts a simple relation between the Dirac and Majorana phases. We also
consider the possibility of certain relations between the CP-violating phases
in the quark and lepton sectors.Comment: 34 pages, no figures; v3: version appeared in JHE
CP-violating asymmetry in in the Skyrme model
We study the CP-violating asymmetry in nonleptonic decay .
By employing the Skyrme model to calculate this decay amplitude contributed by
the gluonic diploe operator, we find a possible large CP-violating asymmetry
could be expected, which is consistent with the previous study.Comment: LaTeX file, To appear in J Phys G: Nucl Phys and Part Phy
Neutrino Physics, Superbeams, and the Neutrino Factory
We summarize what has been learned about the neutrino mass spectrum and
neutrino mixing, identify interesting open questions that can be answered by
accelerator neutrino facilities of the future, and discuss the importance and
physics of answering them.Comment: To appear in the Proceedings of the 4th International Workshop on
Neutrino Factories (Nu Fact 02). LaTeX, 10 pages, 1 eps figur
Neutralino Annihilation at the Galactic Center Revisited
The annihilation of neutralino dark matter in the Galactic Center (GC) may
result in radio signals that can be used to detect or constrain the dark matter
halo density profile or dark matter particle properties. At the Galactic
Center, the accretion flow onto the central Black Hole (BH) sustains strong
magnetic fields that can induce synchrotron emission by electrons and positrons
generated in neutralino annihilations during advection onto the BH. Here we
reanalyze the radiative processes relevant for the neutralino annihilation
signal at the GC, with realistic assumptions about the accretion flow and its
magnetic properties. We find that neglecting these effects, as done in previous
papers, leads to the incorrent electron and photon spectra. We find that the
magnetic fields associated with the flow are significantly stronger than
previously estimated. We derive the appropriate equilibrium distribution of
electrons and positron and the resulting radiation, considering adiabatic
compression in the accretion flow, inverse Compton scattering off synchrotron
photons (synchrotron self-Compton scattering), and synchrotron self-absorption
of the emitted radiation. We derive the signal for a Navarro-Frenk-White (NFW)
dark matter halo profile and a NFW profile with a dark matter spike due to the
central BH. We find that the observed radio emission from the GC is
inconsistent with the scenario in which a spiky distribution of neutralinos is
present. We discuss several important differences between our calculations and
those previously presented in the literature.Comment: 19 pages, 11 eps figures, version accepted for publication in JCA
A "Littlest Higgs" Model with Custodial SU(2) Symmetry
In this note, a ``littlest higgs'' model is presented which has an
approximate custodial SU(2) symmetry. The model is based on the coset space
. The light pseudo-goldstone bosons of the theory
include a {\it single} higgs doublet below a TeV and a set of three
triplets and an electroweak singlet in the TeV range. All of these scalars
obtain approximately custodial SU(2) preserving vacuum expectation values. This
model addresses a defect in the earlier moose
model, with the only extra complication being an extended top sector. Some of
the precision electroweak observables are computed and do not deviate
appreciably from Standard Model predictions. In an S-T oblique analysis, the
dominant non-Standard Model contributions are the extended top sector and higgs
doublet contributions. In conclusion, a wide range of higgs masses is allowed
in a large region of parameter space consistent with naturalness, where large
higgs masses requires some mild custodial SU(2) violation from the extended top
sector.Comment: 22 pages + 8 figures; JHEP style, added references and extra
discussion on size of T contributions, as well as some other minor
clarifications. Version to appear in JHE
Omega and AntiOmega production in Pb+Pb and p+p collisions at 30, 40 and 158 AGeV
We report preliminary results on Omega and AntiOmega production in central
Pb+Pb collisions at 30, 40 and 158 AGeV and p + p interactions at 158 GeV. The
midrapidity AntiOmega/Omega ratio is estimated to be 0.45 +- 0.05 and 0.41 +-
0.18 for central Pb+Pb collisions at 158 and 40 AGeV, respectively. The
corresponding value for 158 GeV p+p interactions is 0.67 +- 0.62. For central
Pb+Pb collisions at 158 AGeV fully corrected distributions are obtained. The
inverse slope parameters of the transverse mass spectrum and total yields are
T(Omega) = 276 +- 23 MeV, = 0.47 +- 0.07 and T(AntiOmega) = 285 +- 39
MeV, = 0.15 +- 0.02.Comment: Contribution to the proceedings of "Strangeness in Quark Matter 2003"
(March 2003, Atlantic Beach NC, USA), to be published in Journal of Physics
G., 6 pages, 6 figure
The process in topcolor-assisted technicolor models
In the context of topcolor-assisted technicolor (TC2) models, we consider the
process and calculate the cross section of
this process at leading order.It is shown that the extra U(1) gauge boson
predicted by TC2 models can give significant contributions to the
process , which may be detected
in the future high energy linear collider(LC) experiments.Comment: latex files,9 pages, 3 figure
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