Search results for "VIOLATION"
showing 10 items of 540 documents
Search for the radiative decay B0→γ
2005
We perform a search for the exclusive radiative decay B0→γ, which is dominated by b̄d annihilation, in a sample of 124×106 BB̄ events collected with the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring at SLAC. No significant signal is seen. We set an upper limit on the branching fraction of B(B0→γ)<8. 5×10-7 at the 90% confidence level. © 2005 The American Physical Society.
CP violating lepton asymmetries in left-right models
1998
Lepton charge asymmetries can be used as an alternative means of searching for new physics. They are interesting because they are small in the Standard Model and therefore, necessarily evidence new physics. In this work we explore the use of lepton asymmetries as a probe of the flavour structure of the left-right symmetric model with spontaneous CP violation. We find that new physics may enhance the magnitude of $a_{SL}$ up to the precent level within the appropiate parameter space.
Electric dipole moments from flavor-changing supersymmetric soft terms
2008
The standard model predictions for the hadronic electric dipole moments (EDMs) are well far from the present experimental resolutions, thus, the EDMs represent very clean probes of New Physics (effects. Especially, within a minimal supersymmetric standard model framework with flavor-changing (but not necessarily CP-violating) soft terms, large and potentially visible effects to the EDMs are typically expected. In this paper we point out that, beyond-leading-order effects, so far neglected in the literature, dominate over the leading-order effects in large regions of the parameter space; hence, their inclusion in the evaluation of the hadronic EDMs is unavoidable.
Mixing asymmetries inBmeson systems, the D0 like-sign dimuon asymmetry, and generic new physics
2015
The measurement of a large like-sign dimuon asymmetry $A^b_{SL}$ by the D0 experiment at the Tevatron departs noticeably from Standard Model expectations and it may be interpreted as a hint of physics beyond the Standard Model contributing to $\Delta B\neq 0$ transitions. In this work we analyse how the natural suppression of $A^b_{SL}$ in the SM can be circumvented by New Physics. We consider generic Standard Model extensions where the charged current mixing matrix is enlarged with respect to the usual $3\times 3$ unitary Cabibbo-Kobayashi-Maskawa matrix, and show how, within this framework, a significant enhancement over Standard Model expectations for $A^b_{SL}$ is easily reachable throu…
Neutrinos that violate CPT, and the experiments that love them
2002
Recently we proposed a framework for explaining the observed evidence for neutrino oscillations without enlarging the neutrino sector, by introducing CPT violating Dirac masses for the neutrinos. In this paper we continue the exploration of the phenomenology of CPT violation in the neutrino sector. We show that our CPT violating model fits the existing SuperKamiokande data at least as well as the standard atmospheric neutrino oscillation models. We discuss the challenge of measuring CP violation in a neutrino sector that also violates CPT. We point out that the proposed off-axis extension of MINOS looks especially promising in this regard. Finally, we describe a method to compute CPT violat…
Superbeam studies at CERN
2003
Abstract A conventional low-energy neutrino beam of great intensity could be produced by the Super Proton Linac at CERN as a first stage of a Neutrino Factory. Water Cherenkov and liquid scintillator detectors are studied as possible candidates for a neutrino oscillation experiment which could improve our current knowledge of the atmospheric parameters Δmatm2, θ23 and measure or severely constrain θ13. It is also shown that a very large water detector could eventually observe leptonic CP violation.
Physics of Massive Neutrinos
2004
I summarize the present status of global analyses of neutrino oscillations, including the most recent KamLAND and K2K data, as well as the latest solar and atmospheric neutrino fluxes. I give the allowed ranges of the three--flavour oscillation parameters from the current worlds' global neutrino data sample, their best fit values and discuss the small parameters DeltaM_solar/DeltaM_atm and sin^2 theta_13, which characterize the strength of CP violation in neutrino oscillations. I briefly discuss neutrinoless double beta decay and the LSND neutrino oscillation hint, as well as the robustness of the neutrino oscillation results in the presence of non-standard physics.
Updated Standard Model Prediction for ε′/ε
2018
Abstract A recent lattice evaluation of e ′ / e , finding a 2.1 σ deviation from the experimental value, has revived the old debate about a possible e ′ / e anomaly. The unfounded claims of a too low Standard Model prediction are based on incorrect estimates that neglect the long-distance re-scattering of the final pions in K → 2 π . In view of the current situation, we have recently updated the Standard Model calculation, including all known short- and long-distance contributions. Our result, Re ( e ′ / e ) = ( 15 ± 7 ) ⋅ 10 − 4 [H. Gisbert and A. Pich, “Direct CP violation in K 0 → π π : Standard Model Status”, Rept. Prog. Phys. 81 (2018) no. 7, 076201 arXiv:1712.06147 [hep-ph] .], is in …
Measurement of theCP-violation parameter ofB0mixing and decay withpp¯→μμXdata
2006
We measure the dimuon charge asymmetry A in p (p) over bar collisions at a center of mass energy root s=1960 GeV. The data was recorded with the D0 detector and corresponds to an integrated luminosity of approximately 1.0 fb(-1). Assuming that the asymmetry A is due to asymmetric B-0 (B) over bar (0) mixing and decay, we extract the CP-violation parameter of B-0 mixing and decay: ((epsilon B0))/(1+vertical bar epsilon B0 vertical bar 2)=(AB0)/(4)= -0.0023 +/- 0.0011(stat)+/- 0.0008(syst).A(B)(0) is the dimuon charge asymmetry from decays of B-0(B) over bar (0) pairs. The general case, with CP violation in both B-0 and B-s(0) systems, is also considered. Finally we obtain the forward-backwar…
Electromagnetism in nonleptonic weak interactions
2000
16 páginas, 1 figura.-- PACS: 11.30.Rd; 13.25.Es; 13.40.Ks.-- arXiv:hep-ph/0006172v2