272 research outputs found
Mixing-induced CP violating sources for electroweak baryogenesis from a semiclassical approach
The effects of flavor mixing in electroweak baryogenesis is investigated in a
generalized semiclassical WKB approach. Through calculating the nonadiabatic
corrections to the particle currents it is shown that extra CP violation
sources arise from the off-diagonal part of the equation of motion of particles
moving inside the bubble wall. This type of mixing-induced source is of the
first order in derivative expansion of the Higgs condensate, but is oscillation
suppressed. The numerical importance of the mixing-induced source is discussed
in the Minimal Supersymmetric Standard Model and compared with the source term
induced by semiclassical force. It is found that in a large parameter space
where oscillation suppression is not strong enough, the mixing-induced source
can dominate over that from the semiclassical force.Comment: 19 pp, 2 figs, 1 table, some comments added, to appear in
Eur.Phys.J.
Unitarity constraints on charged pion photoproduction at large p_perp
Around , the coupling to the channel
leads to a good accounting of the charged pion exclusive photoproduction cross
section in the energy range 3 10 GeV, where experimental data
exist. Starting from a Regge Pole approach that successfully describes vector
meson production, the singular part of the corresponding box diagrams (where
the intermediate vector meson-baryon pair propagates on-shell) is evaluated
without any further assumptions (unitarity). Such a treatment provides an
explanation of the scaling of the cross section. Elastic rescattering
of the charged pion improves the basic Regge pole model at forward and backward
angles.Comment: 5 pages; 6 figure
Photoproduction of charm near threshold
Charm and bottom production near threshold is sensitive to the multi-quark,
gluonic, and hidden-color correlations of hadronic and nuclear wavefunctions in
QCD since all of the target's constituents must act coherently within the small
interaction volume of the heavy quark production subprocess. Although such
multi-parton subprocess cross sections are suppressed by powers of ,
they have less phase-space suppression and can dominate the contributions of
the leading-twist single-gluon subprocesses in the threshold regime. The small
rates for open and hidden charm photoproduction at threshold call for a
dedicated facility.Comment: 5 pages 5 figures Changes: 1- Added refs 24,25; 2- Added two
sentences, top of column 2 of page 3, on the definition of x, its range and
the domain of validity of the mode
Transient domain walls and lepton asymmetry in the Left-Right symmetric model
It is shown that the dynamics of domain walls in Left-Right symmetric models,
separating respective regions of unbroken SU(2)_L and SU(2)_R in the early
universe, can give rise to baryogenesis via leptogenesis. Neutrinos have a
spatially varying complex mass matrix due to CP-violating scalar condensates in
the domain wall. The motion of the wall through the plasma generates a flux of
lepton number across the wall which is converted to a lepton asymmetry by
helicity-flipping scatterings. Subsequent processing of the lepton excess by
sphalerons results in the observed baryon asymmetry, for a range of parameters
in Left-Right symmetric models.Comment: v2 version accepted for publication in Phys. Rev. D. Discussion in
Introduction and Conclusion sharpened. Equation (12) corrected. 16 pages, 3
figure files, RevTeX4 styl
and in the Standard Model and new bounds on R parity violation
We study the pure penguin decays and .
Using QCD factorization, we find . For the pure penguin annihilation process
, analyzed here for the first time, . The smallness of these decays in
the Standard Model makes them sensitive probes for new physics. From the upper
limit of ,we find constraints on R parity violating couplings, , and for . Our new bounds on
are one order of magnitude stronger than
before. Within the available upper bounds for , and
, we find that could
be enhanced to . Experimental searches for these decays
are strongly urged.Comment: 5 pages, 3 figures embede
Effects of Large CP-violating Soft Phases on Supersymmetric Electroweak Baryogenesis
We revisit the results of recent electroweak baryogenesis calculations and
include all allowed large CP-violating supersymmetric phases. If the phases are
large, the resulting baryon asymmetry can be considerably larger than the
observed value . Much of the asymmetry must
therefore be washed out, and we argue that the upper bound on the light Higgs
mass is larger than the value reported in previous work.Comment: 15 pages, 3 figure
Baryogenesis, Electric Dipole Moments and Dark Matter in the MSSM
We study the implications for electroweak baryogenesis (EWB) within the
minimal supersymmetric Standard Model (MSSM) of present and future searches for
the permanent electric dipole moment (EDM) of the electron, for neutralino dark
matter, and for supersymmetric particles at high energy colliders. We show that
there exist regions of the MSSM parameter space that are consistent with both
present two-loop EDM limits and the relic density and that allow for successful
EWB through resonant chargino and neutralino processes at the electroweak phase
transition. We also show that under certain conditions the lightest neutralino
may be simultaneously responsible for both the baryon asymmetry and relic
density. We give present constraints on chargino/neutralino-induced EWB implied
by the flux of energetic neutrinos from the Sun, the prospective constraints
from future neutrino telescopes and ton-sized direct detection experiments, and
the possible signatures at the Large Hadron Collider and International Linear
Collider.Comment: 32 pages, 10 figures; version to appear on JHE
Hadron resonances generated from the dynamics of the lightest scalar ones
We have studied the interactions of the scalar resonances f_0(980) and
a_0(980) with the vector resonance \phi(1020) and with the lightest
pseudoscalars \pi, K, \eta and \eta'. We first obtain the interaction kernels
without including any new free parameter. Afterwards, the interaction kernels
are unitarized and the final S-wave amplitudes result. We find that these
interactions are very rich and generate a large amount of pseudoscalar
resonances including the K(1460), \pi(1300), \pi(1800), \eta(1475) and X(1835)
resonances. The f_0(980)\phi(1020) self-interactions give rise to the
\phi(2170) resonance. For realistic choices of the parameters we also obtain an
isovector companion in the same mass region from the a_0(980) \phi(1020)
interactions.Comment: 4 pafes, 4 figures. Invited talk at QCD 10 (25th anniversary), 15th
International QCD Conference, 28th June - 3rd July 2010 Montpellier (France).
To be published in Nucl. Phys. B (Proc. Suppl.
Structure of the Quark Propagator at High Temperature
In the high temperature, chirally invariant phase of QCD, the quark
propagator is shown to have two sets of poles with different dispersion
relations. A reflection property in momentum space relates all derivatives at
zero-momentum of the particle and hole energies, the particle and hole damping
rates, and the particle and hole residues. No use is made of perturbation
theory.Comment: 8 pages, Latex twocolum
Towards a Nonequilibrium Quantum Field Theory Approach to Electroweak Baryogenesis
We propose a general method to compute -violating observables from
extensions of the standard model in the context of electroweak baryogenesis. It
is alternative to the one recently developed by Huet and Nelson and relies on a
nonequilibrium quantum field theory approach. The method is valid for all
shapes and sizes of the bubble wall expanding in the thermal bath during a
first-order electroweak phase transition. The quantum physics of -violation
and its suppression coming from the incoherent nature of thermal processes are
also made explicit.Comment: 19 pages, 1 figure available upon e-mail reques
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