Search results for " magnitude"
showing 10 items of 407 documents
Spontaneous CP violation and the B0 system
1998
We investigate effects of spontaneous breakdown of CP in $B^0_{d,s}-\overline{B^0}_{d,s}$ systems in left-right symmetric models. Assuming that the left-right contribution to the $B^0-\overline{B^0}$ matrix element $M_{12}$ can be at most equal to the standard model one we obtain a new lower bound, $M_H\gsim 12$ TeV, on the flavour changing Higgs boson mass. Most importantly, the convention independent parameter $Re(\overline{\epsilon}_B),$ which measures the amount of $\Delta B=2$ CP violation, can be enhanced by a factor of four or more for $B^0_d$ and almost by two orders of magnitude for $B^0_s$ systems when compared with the Standard Model predictions. Therefore, interesting possibilit…
Minijet and transverse energy production in the BFKL regime
1996
Minijet production in hadronic and nuclear collisions through a BFKL pomeron ladder is studied for the energies of the future LHC heavy-ion collisions. We use unintegrated gluon densities compatible with the small-$x$ increase of parton distributions observed at HERA. We show that at LHC energies the BFKL minijet and transverse energy production is at most of the same order of magnitude as that in the collinear factorization approach.
Search for direct CP-violation in K±→π±π0π0 decays
2006
Abstract A search for direct CP-violation in K ± → π ± π 0 π 0 decay based on 47.14 million events has been performed by the NA48/2 experiment at the CERN SPS. The asymmetry in the Dalitz plot linear slopes A g = ( g + − g − ) / ( g + + g − ) is measured to be A g = ( 1.8 ± 2.6 ) × 10 −4 . The design of the experiment and the method of analysis provide good control of instrumental charge asymmetries in this measurement. The precision of the result is limited by statistics and is almost one order of magnitude better than that of previous measurements by other experiments.
Search for the decayD0→γγand measurement of the branching fraction forD0→π0π0
2012
We search for the rare decay of the D^0 meson to two photons, D^0→γγ, and present a measurement of the branching fraction for a D^0 meson decaying to two neutral pions, B(D^0→π^0π^0). The data sample analyzed corresponds to an integrated luminosity of 470.5 fb^(-1) collected by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at SLAC. We place an upper limit on the branching fraction, B(D^0→γγ)<2.2×10^(-6), at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find B(D^0→π^0π^0)=(8.4±0.1±0.4±0.3)×10^(-4).
Coherent muon-electron conversion in the dualized standard model
2000
Muon-electron conversion in nuclei is considered in the framework of the Dualized Standard Model. The ratio $B_{\mu-e}$ of the conversion rate to the total muon capture rate is derived, and computed for several nuclei in a parameter-free calculation using parameters previously determined in different physical contexts. The values obtained all lie within the present experimental bounds, but some are so close as to seem readily accessible to experiments already being planned. Similar considerations are applied also to muon-electron conversion in muonium but give rates many orders of magnitude below the present experiment limit.
Improved $K_{e3}$ radiative corrections sharpen the $K_{\mu 2}$--$K_{l3}$ discrepancy
2021
The measurements of $V_{us}$ in leptonic $(K_{\mu 2})$ and semileptonic $(K_{l3})$ kaon decays exhibit a $3\sigma$ disagreement, which could originate either from physics beyond the Standard Model or some large unidentified Standard Model systematic effects. Clarifying this issue requires a careful examination of all existing Standard Model inputs. Making use of a newly-proposed computational framework and the most recent lattice QCD results, we perform a comprehensive re-analysis of the electroweak radiative corrections to the $K_{e3}$ decay rates that achieves an unprecedented level of precision of $10^{-4}$, which improves the current best results by almost an order of magnitude. No larg…
Constraining Majorana neutrino electromagnetic properties from the LMA-MSW solution of the solar neutrino problem
2002
In this paper we use solar neutrino data to derive stringent bounds on Majorana neutrino transition moments (TMs). Should such be present, they would contribute to the neutrino--electron scattering cross section and hence alter the signal observed in Super-Kamiokande. Motivated by the growing robustness of the LMA-MSW solution of the solar neutrino problem indicated by recent data, and also by the prospects of its possible confirmation at KamLAND, we assume the validity of this solution, and we constrain neutrino TMs by using the latest global solar neutrino data. We find that all elements of the TM matrix can be bounded at the same time. Furthermore, we show how reactor data play a complem…
Confusing non-standard neutrino interactions with oscillations at a neutrino factory
2002
Most neutrino mass theories contain non-standard interactions (NSI) of neutrinos which can be either non-universal (NU) or flavor-changing (FC). We study the impact of such interactions on the determination of neutrino mixing parameters at a neutrino factory using the so-called ``golden channels'' \pnu{e}\to\pnu{\mu} for the measurement of \theta_{13}. We show that a certain combination of FC interactions in neutrino source and earth matter can give exactly the same signal as oscillations arising due to \theta_{13}. This implies that information about \theta_{13} can only be obtained if bounds on NSI are available. Taking into account the existing bounds on FC interactions, this leads to a …
Radiative corrections for Dalitz decays of π0, η(′) and Σ0
2020
Abstract We briefly summarize current experimental and theoretical results on the π 0 Dalitz decay, and provide a new value for the ratio R = Γ ( π 0 → e + e − γ ( γ ) ) / Γ ( π 0 → γ γ ) = 11.978 ( 6 ) × 10 − 3 , which is by two orders of magnitude more precise than the current PDG average. This value is obtained using the complete set of the next-to-leading-order radiative corrections in the QED sector, and incorporates up-to-date values of the π 0 -transition-form-factor slope. Furthermore, we present the complete set of radiative corrections for the Dalitz decays η ( ′ ) → l + l − γ beyond the soft-photon approximation. The corrections inevitably depend on the η ( ′ ) → γ ⁎ γ ( ⁎ ) tran…
A trigger system for measurements of proton-induced rare hadronic reactions around Tp=400MeV
2008
Abstract We developed a trigger system for the measurement of proton-induced rare hadronic reactions around the beam kinetic energy T p = 400 MeV based on highly segmented trigger scintillation detectors and programmable logic modules. The trigger system was designed to enhance events with the negative-pion production by the difference of the curvatures of the particle tracks in a magnetic field. Since the production cross-section of the negative-pion by the proton-induced reactions was smaller by about 3 orders of magnitude than the total cross-section around the beam energy, we expected large reduction of the trigger rate by the negative-pion selection. The construction of the trigger sys…