Search results for "Proton"
showing 10 items of 5886 documents
The PANDA Barrel DIRC detector
2014
Abstract The PANDA experiment at the new Facility for Antiproton and Ion Research in Europe (FAIR) at GSI, Darmstadt, will study fundamental questions of hadron physics and QCD using high-intensity cooled antiproton beams with momenta between 1.5 and 15 GeV/c. Efficient Particle Identification for a wide momentum range and the full solid angle is required for reconstructing the various physics channels of the PANDA program. Hadronic Particle Identification in the barrel region of the detector will be provided by a DIRC counter. The design is based on the successful BABAR DIRC with important improvements, such as focusing optics and fast photon timing. Several of these improvements, includin…
A unitary isobar model for pion photo- and electroproduction on the proton up to 1 GeV
1998
A new operator for pion photo- and electroproduction has been developed for nuclear applications at photon equivalent energies up to 1 GeV. The model contains Born terms, vector mesons and nucleon resonances ($P_{33}(1232)$, $P_{11}(1440)$, $D_{13}(1520)$, $S_{11}(1535)$, $F_{15}(1680)$, and $D_{33}(1700)$). The resonance contributions are included taking into account unitarity to provide the correct phases of the pion photoproduction multipoles. The $Q^2$ dependence of electromagnetic resonance vertices is described with appropriate form factors in the electromagnetic helicity amplitudes. Within this model we have obtained good agreement with the experimental data for pion photo- and elect…
Photoproduction of theωmeson on the proton near threshold
2015
An experimental study of omega photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The gamma p -> omega p differential cross sections are measured from threshold to the incident-photon energy E-gamma = 1.40 GeV (W = 1.87 GeV for the center-of-mass energy) with 15-MeV binning in E-gamma and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics aspects. As an example, an estimation of the omega N scattering length alpha(omega p) is provided.
SU(5)-inspired double beta decay
2015
The short-range part of the neutrinoless double beta amplitude is generated via the exchange of exotic particles, such as charged scalars, leptoquarks and/or diquarks. In order to give a sizable contribution to the total decay rate, the masses of these exotics should be of the order of (at most) a few TeV. Here, we argue that these exotics could be the “light” (i.e., weak-scale) remnants of some B – L violating variants of SU(5). We show that unification of the standard model gauge couplings, consistent with proton decay limits, can be achieved in such a setup without the need to introduce supersymmetry. Since these nonminimal SU(5)-inspired models violate B – L, they generate Majorana neut…
The Minimal Supersymmetric Model without a mu term
2002
We propose a supersymmetric extension of the standard model which is a realistic alternative to the MSSM, and which has several advantages. No ``mu'' supersymmetric Higgs/Higgsino mass parameter is needed for sufficiently heavy charginos. An approximate U(1) R symmetry naturally guarantees that tan beta is large, explaining the top/bottom quark mass hierarchy. This symmetry also suppresses supersymmetric contributions to anomalous magnetic moments, b to s gamma, and proton decay, and these processes place no lower bounds on superpartner masses, even at large tan beta. The soft supersymmetry breaking mass parameters can easily be obtained from either gauge or Planck scale mediation, without …
Measurements of the decaysB0→D¯0pp¯,B0→D¯*0pp¯,B0→D−pp¯π+, andB0→D*−pp¯π+
2006
We present measurements of branching fractions of $B^0$ decays to multi-body final states containing protons, based on 232 million $\Upsilon(4S)\to B\bar{B}$ decays collected with the BaBar detector at the SLAC PEP-II asymmetric-energy $B$ factory. We measure the branching fractions ${\cal B}(B^0 \to \bar{D}^0\proton\antiproton)=(1.13\pm0.06\pm0.08)\times 10^{-4}$, ${\cal B}(B^0 \to \bar{D}^{*0}\proton\antiproton)=(1.01\pm0.10\pm0.09)\times 10^{-4}$, ${\cal B}(B^0 \to D^{-}\proton\antiproton\pi^+)=(3.38\pm0.14\pm0.29)\times 10^{-4}$, and ${\cal B}(B^0 \to D^{*-}\proton\antiproton\pi^+)=(4.81\pm0.22\pm0.44)\times 10^{-4}$ where the first error is statistical and the second systematic. We pre…
Nonlinear corrections to the DGLAP equations in view of the HERA data
2002
The effects of the first nonlinear corrections to the DGLAP evolution equations are studied by using the recent HERA data for the structure function $F_2(x,Q^2)$ of the free proton and the parton distributions from CTEQ5L and CTEQ6L as a baseline. By requiring a good fit to the H1 data, we determine initial parton distributions at $Q_0^2=1.4$ GeV$^2$ for the nonlinear scale evolution. We show that the nonlinear corrections improve the agreement with the $F_2(x,Q^2)$ data in the region of $x\sim 3\cdot 10^{-5}$ and $Q^2\sim 1.5$ GeV$^2$ without paying the price of obtaining a worse agreement at larger values of $x$ and $Q^2$. For the gluon distribution the nonlinear effects are found to play…
Multiplicity dependence of charged pion, kaon, and (anti)proton production at large transverse momentum in p–Pb collisions at sNN=5.02 TeV
2016
The production of charged pions, kaons and (anti)protons has been measured at mid-rapidity ($-0.5 10$ GeV/$c$), the particle ratios are consistent with those reported for pp and Pb-Pb collisions at the LHC energies. At intermediate $p_{\rm T}$ the (anti)proton $R_{\rm pPb}$ shows a Cronin-like enhancement, while pions and kaons show little or no nuclear modification. At high $p_{\rm T}$ the charged pion, kaon and (anti)proton $R_{\rm pPb}$ are consistent with unity within statistical and systematic uncertainties.
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…
Vector current conservation and neutrino emission from singlet-paired baryons in neutron stars
2006
Neutrino emission caused by singlet Cooper pairing of baryons in neutron stars is recalculated by accurately taking into account for conservation of the vector weak currents. The neutrino emissivity via the vector weak currents is found to be several orders of magnitude smaller than that obtained before by different authors. This makes unimportant the neutrino radiation from singlet pairing of protons or hyperons.