1,587 research outputs found
SUSY-QCD Effect on Top-Charm Associated Production at Linear Collider
We evaluate the contribution of SUSY-QCD to top-charm associated production
at next generation linear colliders. Our results show that the production cross
section of the process could be as large as 0.1
fb, which is larger than the prediction of the SM by a factor of .Comment: version to appear in PR
Effects of azimuth-symmetric acceptance cutoffs on the measured asymmetry in unpolarized Drell-Yan fixed target experiments
Fixed-target unpolarized Drell-Yan experiments often feature an acceptance
depending on the polar angle of the lepton tracks in the laboratory frame.
Typically leptons are detected in a defined angular range, with a dead zone in
the forward region. If the cutoffs imposed by the angular acceptance are
independent of the azimuth, at first sight they do not appear dangerous for a
measurement of the cos(2\phi)-asymmetry, relevant because of its association
with the violation of the Lam-Tung rule and with the Boer-Mulders function. On
the contrary, direct simulations show that up to 10 percent asymmetries are
produced by these cutoffs. These artificial asymmetries present qualitative
features that allow them to mimic the physical ones. They introduce some
model-dependence in the measurements of the cos(2\phi)-asymmetry, since a
precise reconstruction of the acceptance in the Collins-Soper frame requires a
Monte Carlo simulation, that in turn requires some detailed physical input to
generate event distributions. Although experiments in the eighties seem to have
been aware of this problem, the possibility of using the Boer-Mulders function
as an input parameter in the extraction of Transversity has much increased the
requirements of precision on this measurement. Our simulations show that the
safest approach to these measurements is a strong cutoff on the Collins-Soper
polar angle. This reduces statistics, but does not necessarily decrease the
precision in a measurement of the Boer-Mulders function.Comment: 13 pages, 14 figure
Pleiotrophin is a key switch of human monocytes and bone marrow stem cells into endotherlial-like cells for angiogenesis in tumor growth
CP violation in BâÏKs in a model III two Higgs doublet model
The mixing induced time dependent CP asymmetry, direct CP asymmetry,
and branching ratio in BâÏKs in a model III 2HDM are calculated,
in particular, neutral Higgs boson contributions are included. It is shown
that satisfying all the relevant experimental constraints, for time dependent
CP asymmetry SÏK the model III can agree with the present data, SÏk =
â0.39±0.41, within the 1Ï error, and the direct CP asymmetry which is zero
in SM can be about â8% ⌠â20% in the reasonable regions of parameters
Saturation and Wilson Line Distributions
We introduce a Wilson line distribution function bar{W}_tau(v) to study gluon
saturation at small Feynman x_F, or large tau=ln(1/x_F). This new distribution
can be obtained from the distribution W_tau(alpha) of the Color Glass
Condensate model and the JIMWLK renormalization group equation. bar{W}_tau(v)
is physically more relevant, and mathematically simpler to deal with because of
unitarity of the Wilson line v. A JIMWLK equation is derived for bar{W}_tau(v);
its properties are studied. These properties are used to complete Mueller's
derivation of the JIMWLK equation, though for bar{W}_tau(v) and not
W_tau(alpha). They are used to derive a generalized Balitsky-Kovchegov equation
for higher multipole amplitudes. They are also used to compute the unintegrated
gluon distribution at x_F=0, yielding a completely flat spectrum in transverse
momentum squared k^2, with a known height. This is similar but not identical to
the mean field result at small k^2.Comment: One reference and two short comments added. To appear in Physical
Revies
A multiphase strategy for realizing green cathodoluminescence in 12CaO center dot 7Al(2)O(3)-CaCeAl3O7:Ce3+,Tb3+ conductive phosphor
Magnetic-interference patterns in Josephson junctions with d+is symmetry
The magnetic interference pattern and the spontaneous flux in unconventional
Josephson junctions of superconductors with d+is symmetry are calculated for
different reduced junction lengths and the relative factor of the d and s wave
components. This is a time reversal broken symmetry state. We study the
stability of the fractional vortex and antivortex which are spontaneously
formed and examine their evolution as we change the length and the relative
factor of d and s wave components. The asymmetry in the field modulated
diffraction pattern exists for lengths as long as L=10\lambda_J.Comment: 8 pages, 6 eps files, submitted to PR
Discovery and Observations of ASASSN-13db, an EX Lupi-Type Accretion Event on a Low-Mass T Tauri Star
We discuss ASASSN-13db, an EX Lupi-type ("EXor") accretion event on the young
stellar object (YSO) SDSS J051011.01032826.2 (hereafter SDSSJ0510)
discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN). Using
archival photometric data of SDSSJ0510 we construct a pre-outburst spectral
energy distribution (SED) and find that it is consistent with a low-mass class
II YSO near the Orion star forming region ( pc). We present
follow-up photometric and spectroscopic observations of the source after the
5.4 magnitude outburst that began in September 2013 and ended
in early 2014. These data indicate an increase in temperature and luminosity
consistent with an accretion rate of yr,
three or more orders of magnitude greater than in quiescence. Spectroscopic
observations show a forest of narrow emission lines dominated by neutral
metallic lines from Fe I and some low-ionization lines. The properties of
ASASSN-13db are similar to those of the EXor prototype EX Lupi during its
strongest observed outburst in late 2008.Comment: 14 pages, 4 figures, 1 table. Updated May 2014 to reflect changes in
the final version published in ApJL. Photometric data presented in this
submission are included as ancillary files. For a brief video explaining this
paper, see http://youtu.be/yRCCrNJnvt
Associated Production of a Z Boson and a Single Heavy-Quark Jet
The leading-order process for the production of a Z boson and a heavy-quark
jet at hadron colliders is gQ -> ZQ (Q=c,b). We calculate this cross section at
next-to-leading order at the Tevatron and the LHC, and compare it with other
sources of ZQ events. This process is a background to new physics, and can be
used to measure the heavy-quark distribution function.Comment: 15 pages, 9 figures. Version to appear in Phys. Rev.
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