125760852
Diffractive vector meson production at intermediate energies.
55047377
Optical characterization of n = 1.03 silica aerogel used as radiator in the RICH of HERMES
The optical properties of silica aerogel tiles with a refractive index of 1.03 and dimensions 11]11] 1c m 3, produced by the Matsushita Electric Works (Japan), have been measured in the wavelength range from 200 to 900 nm. The tiles are used as one of the two radiators of the ring imaging Cherenkov counter of the HERMES experiment at DESY-HERA. The transmittance of light has been measured on 200 tiles by means of a double beam spectrophotometer. The light trans#ectance and re#ectance have been measured on one tile by means of a single-beam spectrophotometer and an integrating re#ecting sphere. Typical values of the measured transmittances at a wavelength j"400 nm are around 0.67. The measured trans#ectance increases almost linearly from 0.4 to 0.96 in the interval 200}300 nm, and remains nearly constant at the value 0.95 in the complementary j-range. The measured re#ectance, mostly con"ned below 400 nm, is completely interpretable as backscattering from inside the aerogel, revealing an absence of light re#ection at the aerogel surfaces. The transmittance data have been "tted with the Hunt formula, whose parameters have been used to evaluate the number of unscattered and scattered Cherenkov photons produced by aerogel. For stacks of 5 tiles and quantum
15360804
SUSY Searches in All-Hadronic States with Large MET at the LHC
The CMS and ATLAS search strategy for SUSY in inclusive multijet plus high missing transverse energy final states is reviewed. This canonical SUSY signature may be a viable discovery channel for low mass SUSY in the early phase of the LHC. Methods for Standard Model background estimates, MET studies and filters for instrumental background are presented.
122512363
Exclusive meson production at HERMES
Abstract.Hard exclusive production of mesons in deep-inelastic scattering allows one to probe the so-far unknown Generalized Parton Distributions (GPDs) of the nucleon. The HERMES experiment has measured several different observables in exclusive meson production by scattering the 27.6GeV HERA lepton beam off an internal fixed gaseous target. Recent results on exclusive π+, ρ0 and pion pair production will be presented.
119348282
Sum rules in the CFL phase of QCD at finite density
Abstract We study the asymmetry between the vector current and axial-vector current correlators in the colour–flavour locking (CFL) phase of QCD at finite density. Using Weinberg's sum rules, we compute the decay constant f π of the Goldstone modes and find agreement with previous derivations. Using Das's sum rule, we also estimate the contribution of electromagnetic interactions to the mass of the charged modes. Finally, we comment on low temperature corrections to the effective field theory describing the Goldstone bosons.
119148641
Electroweak symmetry breaking induced by dark matter
Abstract The mechanism behind electroweak symmetry breaking (EWSB) and the nature of dark matter (DM) are currently among the most important issues in high energy physics. Since a natural dark matter candidate is a weakly interacting massive particle or WIMP, with mass around the electroweak scale, it is clearly of interest to investigate the possibility that DM and EWSB are closely related. In the context of a very simple extension of the Standard Model, the inert doublet model, we show that dark matter could play a crucial role in the breaking of the electroweak symmetry. In this model, dark matter is the lightest component of an inert scalar doublet. The coupling of the latter with the Standard Model Higgs doublet breaks the electroweak symmetry at one-loop, a la Coleman–Weinberg . The abundance of dark matter, the breaking of the electroweak symmetry and the constraints from electroweak precision measurements can all be accommodated by imposing (an exact or approximate) custodial symmetry.
118663497
Background reionization history from omniscopes
The measurements of the 21-cm brightness temperature fluctuations from the neutral hydrogen at the Epoch of Reionization should inaugurate the next generation of cosmological observables. In this respect, many works have concentrated on the disambiguation of the cosmological signals from the dominant reionization foregrounds. However, even after perfect foregrounds removal, our ignorance on the background reionization history can significantly affect the cosmological parameter estimation. In particular, the interdependence between the hydrogen ionized fraction, the baryon density and the optical depth to the redshift of observation induce nontrivial degeneracies between the cosmological parameters that have not been considered so far. Using a simple but consistent reionization model, we revisit their expected constraints for a futuristic giant 21-cm omniscope by using for the first time Markov Chain Monte Carlo methods on multiredshift full sky simulated data. Our results agree well with the usual Fisher matrix analysis on the three-dimensional flat sky power spectrum but only when the above-mentioned degeneracies are kept under control. In the opposite situation, Fisher results can be inaccurate. We show that these conditions can be fulfilled by combining cosmic microwave background measurements with multiple observation redshifts probing the beginning of the Epoch of Reionization. This allows a precise reconstruction of the total optical depth, reionization duration and maximal spin temperature. Finally, we discuss the robustness of these results in presence of unresolved ionizing sources. Although most of the standard cosmological parameters remain weakly affected, we find a significant degradation of the background reionization parameter estimation in presence of nuisance ionizing sources.
122397416
Contribution to radiative corrections from decoupling particles
Particles which normally decouple in the large mass limit (i.e., unrelated to the symmetry breaking) may contribute to radiative corrections if their mass ismnew∼MW. We study their effect on various observables.
18340855
Confined hidden vector dark matter
Abstract We argue that the lightest vector bound states of a confining hidden sector communicating with the Standard Model through the Higgs portal are stable and are viable candidates of dark matter. The model is based on an SU ( 2 ) gauge group with a scalar field in its fundamental representation and the stability of the lightest vector bound state results from the existence of a custodial symmetry. As the relic density depends essentially on the scale of confinement in the hidden sector, Λ HS , agreement with WMAP abundance requires Λ HS in the 20–120 TeV range.