2,407 research outputs found
Particle physics catalysis of thermal Big Bang Nucleosynthesis
We point out that the existence of metastable, tau > 10^3 s, negatively
charged electroweak-scale particles (X^-) alters the predictions for lithium
and other primordial elemental abundances for A>4 via the formation of bound
states with nuclei during BBN. In particular, we show that the bound states of
X^- with helium, formed at temperatures of about T=10^8K, lead to the catalytic
enhancement of Li6 production, which is eight orders of magnitude more
efficient than the standard channel. In particle physics models where
subsequent decay of X^- does not lead to large non-thermal BBN effects, this
directly translates to the level of sensitivity to the number density of
long-lived X^-, particles (\tau>10^5 s) relative to entropy of n_{X^-}/s <
3\times 10^{-17}, which is one of the most stringent probes of electroweak
scale remnants known to date.Comment: Some typos correcte
CP-odd effective gluonic Lagrangian in Kobayashi-Maskawa model
Schwinger operator method is applied for studying CP-odd pure gluonic
effective Lagrangian in the Standard Model at three-loop level. The induced
-term vanishes by the same reasons as EDMs of quark and W-boson to
two-loop approximation. A simple way is found to demonstrate these
cancellations. All other terms of the effective Lagrangian acquire
non-vanishing contributions. The effective operator of dimension six, Weinberg
operator, is calculated explicitly. The corresponding contribution to the EDM
of neutron is much smaller than that comes from large distances.Comment: Latex, 12 pages, BUDKERINP 94-2
Sensitivity to new supersymmetric thresholds through flavour and CP violating physics
Treating the MSSM as an effective theory below a threshold scale Lambda, we
study the consequences of having dimension-five operators in the superpotential
for flavour and CP-violating processes. Below the supersymmetric threshold such
terms generate flavour changing and/or CP-odd effective operators of dimension
six composed from the Standard Model fermions, that have the interesting
property of decoupling linearly with the threshold scale, i.e. as 1/(Lambda
m_soft), where m_soft is the scale of soft supersymmetry breaking. The
assumption of weak-scale supersymmetry, together with the stringent limits on
electric dipole moments and lepton flavour-violating processes, then provides
sensitivity to Lambda as high as 10^7-10^9 GeV. We discuss the varying
sensitivity to these scales within several MSSM benchmark scenarios and also
outline the classes of UV physics which could generate these operators.Comment: 28 pages, 9 figure
Lorentz Violation in Supersymmetric Field Theories
We construct supersymmetric Lorentz violating operators for matter and gauge
fields. We show that in the supersymmetric Standard Model the lowest possible
dimension for such operators is five, and therefore they are suppressed by at
least one power of an ultra--violet energy scale, providing a possible
explanation for the smallness of Lorentz violation and its stability against
radiative corrections. Supersymmetric Lorentz noninvariant operators do not
lead to modifications of dispersion relations at high energies thereby escaping
constraints from astrophysical searches for Lorentz violation.Comment: Minor correction
Novel direct detection constraints on light dark matter
All attempts to directly detect particle dark matter (DM) scattering on
nuclei suffer from the partial or total loss of sensitivity for DM masses in
the GeV range or below. We derive novel constraints from the inevitable
existence of a subdominant, but highly energetic, component of DM generated
through collisions with cosmic rays. Subsequent scattering inside conventional
DM detectors, as well as neutrino detectors sensitive to nuclear recoils,
limits the DM-nucleon scattering cross section to be below cm
for both spin-independent and spin-dependent scattering of light DM.Comment: 7 pages revtex4, 3 figures. Version to appear in Phys. Rev. Let
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