Experimental study study of antiproton-proton annihilation into a pair of charged Pi-Mesons or K-Mesons for incident antiproton mementa in the range from 0.72 GeV/c to 2.62 GeV/c

<p>The cross sections for the two antiproton-proton annihilation-in-flight modes,</p> <p>��p + p ��� ��⁺ + ��^-</p> <p>��p + p ��� k⁺ + k^-</p> <p>were measured for fifteen laboratory antiproton beam momenta ranging from 0.72 to 2.62 GeV/c. No magnets were used to determine the charges in the final state. As a result, the angular distributions were obtained in the form [d��/d�� (��_C.M.) + d��/d�� (�� ��� ��_C.M.)] for 45 ��� ��_C.M. ��� 135��. </p> <p>A hodoscope-counter system was used to discriminate against events with final states having more than two particles and antiproton-proton elastic scattering events. One spark chamber was used to record the track of each of the two charged final particles. A total of about 40,000 pictures were taken. The events were analyzed by measuring the laboratory angle of the track in each chamber. The value of the square of the mass of the final particles was calculated for each event assuming the reaction</p> <p>��p + p ��� a pair of particles with equal masses.</p> <p>About 20,000 events were found to be either annihilation into �� ^��-pair or k ^��-pair events. The two different charged meson pair modes were also distinctly separated.</p> <p>The average differential cross section of ��p + p ��� ��⁺ + ��^- varied from ~ 25 ��b/sr at antiproton beam momentum 0.72 GeV/c (total energy in center-of-mass system, ���s = 2.0 GeV) to ~ 2 ��b/sr at beam momentum 2.62 GeV/c (���s = 2.64 GeV). The most striking feature in the angular distribution was a peak at ��_C.M. = 90�� (cos ��_C.M. = 0) which increased with ���s and reached a maximum at ���s ~ 2.1 GeV (beam momentum ~ 1.1 GeV/c). Then it diminished and seemed to disappear completely at ���s ~ 2.5 GeV (beam momentum ~ 2.13 GeV/c). A valley in the angular distribution occurred at cos ��_C.M. ��� 0.4. The differential cross section then increased as cos ��_C.M. approached 1.</p> <p>The average differential cross section for ��p + p ��� k⁺ + k^- was about one third of that of the ��^��-pair mode throughout the energy range of this experiment. At the lower energies, the angular distribution, unlike that of the ��^��-pair mode, was quite isotropic. However, a peak at ��_C.M. = 90�� seemed to develop at ���s ~ 2.37 GeV (antiproton beam momentum ~ 1.82 GeV/c). No observable change was seen at that energy in the ��^��-pair cross section.</p> <p>The possible connection of these features with the observed meson resonances at 2.2 GeV and 2.38 GeV, and its implications, were discussed. </p>

Measurement of K*(892)(0) and K-0 mesons in Al plus Al collisions at 1.9A GeV

A new measurement of subthreshold K*(892)(0) and K-0 production is presented. The experimental data complete the measurement of strange particles produced in Al + Al collisions at 1.9A GeV measured with the FOPI detector at SIS at GSI (Darmstadt). The K*(892)(0)/K-0 yield ratio is found to be 0.0315 +/- 0.006(stat.) +/- 0.012(syst.) and is in good agreement with the transport model prediction. These measurements provide information on the in-medium cross section of K+-pi(-) fusion, which is the dominant process in subthreshold K*(892)(0) production.

Low-Energy Scattering of Heavy-Light Mesons from Nucleons

We study the low-energy scattering of charmed (D) and strange (K) mesons by nucleons. The short-distance part of the interaction is due to quark-gluon interchanges derived from a model that realizes dynamical chiral symmetry breaking and confines color. The quark-gluon interaction incorporates a confining Coulomb-like potential extracted from lattice QCD simulations in Coulomb gauge and a transverse hyperfine interaction consistent with a finite gluon propagator in the infrared. The long-distance part of the interaction is due to single vector (rho, omega) and scalar (sigma) meson exchanges. We show results for scattering cross-sections for isospin I = 0 and I = 1.

First ��K atom lifetime and ��K scattering length measurements

The results of a search for hydrogen-like atoms consisting of �����K�������K�� mesons are presented. Evidence for ��K atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic ��K pairs from their breakup in the same target (178��49178��49) as well as in terms of produced ��K atoms (653��42653��42). Using these results, the analysis yields a first value for the ��K atom lifetime of View the MathML source��=(2.5���1.8+3.0) fs and a first measurement of the S-wave isospin-odd ��K scattering length View the MathML source|a0���|=13|a1/2���a3/2|=(0.11���0.04+0.09)M�����1 (aIaI for isospin I).

Effective mass of kaons in hyperon-rich matter

By including the scalar isovector meson delta, we extend the relativistic mean field model and the one-boson exchange model of changing K-meson in the framework of Schaffner's relativistic mean field model. We re-consider the coupling constants for the interactions between the meson and the baryon and the interactions of the K meson with different mesons as well in various parameter sets. Using our model, we discuss the effective masses of K mesons in the hyperon-rich nuclear matter. We find that the density modification of the K meson mass in the strange nuclear matter is smaller than that in the pure nuclear matter. The influence of the scalar isovector meson 6 on the effective mass of kaon is rather evident. But the extent of the influence is different in different parameter sets.

Nonmesonic weak decay dynamics from proton spectra of Lambda-hypernuclei

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Production of psi(2S) Mesons in ppbar Collisions at 1.96 TeV

We have measured the differential cross section for the inclusive production of psi(2S) mesons decaying to mu^{+} mu^{-1} that were produced in prompt or B-decay processes from ppbar collisions at 1.96 TeV. These measurements have been made using a data set from an integrated luminosity of 1.1 fb^{-1} collected by the CDF II detector at Fermilab. For events with transverse momentum p_{T} (psi(2S)) &gt; 2 GeV/c and rapidity |y(psi(2S))| psi(2S)X) Br(psi(2S) -&gt; mu^{+} mu^{-}) to be 3.29 +- 0.04(stat.) +- 0.32(syst.) nb.

Production of ��(2S) mesons in pp�� collisions at 1.96 TeV

We have measured the differential cross section for the inclusive production of psi(2S) mesons decaying to mu^{+} mu^{-1} that were produced in prompt or B-decay processes from ppbar collisions at 1.96 TeV. These measurements have been made using a data set from an integrated luminosity of 1.1 fb^{-1} collected by the CDF II detector at Fermilab. For events with transverse momentum p_{T} (psi(2S)) > 2 GeV/c and rapidity |y(psi(2S))| psi(2S)X) Br(psi(2S) -> mu^{+} mu^{-}) to be 3.29 +- 0.04(stat.) +- 0.32(syst.) nb.

Search for narrow resonances lighter than �� mesons

We report a search for narrow resonances, produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV, that decay into muon pairs with invariant mass between 6.3 and 9.0 GeV/c^2. The data, collected with the CDF~II detector at the Fermilab Tevatron collider, correspond to an integrated luminosity of 630 pb$^{-1}$. We use the dimuon invariant mass distribution to set 90% upper credible limits of about 1% to the ratio of the production cross section times muonic branching fraction of possible narrow resonances to that of the $\Upsilon(1{\rm S})$ meson.

Properties of l=1 B-1 and B*(2) Mesons

This Letter presents the first strong evidence for the resolution of the excited B mesons B-1 and B-2(*) as two separate states in fully reconstructed decays to B+(*())pi(-). The mass of B-1 is measured to be 5720.6 +/- 2.4 +/- 1.4 MeV/c(2) and the mass difference Delta M between B-2* and B-1 is 26.2 +/- 3.1 +/- 0: 9 MeV/c(2), giving the mass of the B-2* as 5746.8 +/- 2.4 +/- 1.7 MeV/c(2). The production rate for B-1 and B-2* mesons is determined to be a fraction (13.9 +/- 1.9 +/- 3.2)% of the production rate of the B+ meson.

Measurement of semileptonic branching fractions of B mesons to narrow D-** states - art. no. 1711803

Using the data accumulated in 2002-2004 with the D0 detector in proton-antiproton collisions at the Fermilab Tevatron collider with a center-of-mass energy of 1.96 TeV, the branching fractions of the decays B ->(D) over bar (0)(1)(2420)mu(+)nu(mu)X and B ->(D) over bar (*0)(2)(2460)mu(+)nu(mu)X and their ratio have been measured: B (b) over bar -> B)xB(B -> (D) over bar (0)(1)mu(+)nu(mu)X)xB((D) over bar (0)(1)-> D(*-)pi(+))=[0.087 +/- 0.007(stat)+/- 0.014(syst)]%; B((b) over bar -> B)xB(B ->(D) over bar (*0)(2)mu(+)nu(mu)X)xB((D) over bar (*0)(2)-> D(*-)pi(+))=[0.035 +/- 0.007(stat)+/- 0.008(syst)]% and [B(B ->(D) over bar (*0)(2)mu(+)nu(mu)X)xB((D) over bar (*0)(2)-> D(*-)pi(+))]/[B(B ->(D) over bar (0)(1)mu(+)nu(mu)X)xB((D) over bar (0)(1)-> D(*-)pi(+))]=0.39 +/- 0.09(stat)+/- 0.12(syst), where the charge conjugated states are always implied.

Relative rates of B meson decays into psi(2S) and J/psi mesons

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

Off-diagonal helicity density matrix elements for vector mesons produced in polarized e+e- processes

Final-state qq�� interactions give origin to nonzero values of the off-diagonal element ��1,-1 of the helicity density matrix of vector mesons produced in e+e- annihilations, as has been confirmed by recent OPAL data on ��, D*, and K*. New predictions are given for ��1,-1 of several mesons produced at large XE and small pT - i.e., collinear with the parent jet - in the annihilation of polarized e+ and e-; the results depend strongly on the elementary dynamics and allow further nontrivial tests of the standard model.

Nuclear photoproduction of pseudoscalar mesons at forward angles up to 6.0 GeV

The nuclear incoherent �� 0 photoproduction cross section from 12C is evaluated at forward angles in the 4.0 to 6.0 GeV energy range using the multicollisional intranuclear cascade model MCMC. The model incorporates some improvements in comparison with previous versions associated with the momentum distribution (MD) for light nuclei - extracted from the available (e,e ���p) data - as well as the evaluation of the shadowing effects during the photo-nucleus interaction. The final results of the single and double differential cross sections at forward angles are very sensitive to the MD parameterizations due to the Pauli principle, which largely suppresses the cross sections for low momentum transfer. The attenuation of the nuclear cross section due to pion - nucleus final state interactions is approximately 40% (without nuclear shadowing), which is in nice agreement with the predictions from the Glauber model. The single and double �� 0 differential cross sections are presented for possible applications for the interpretation of the inelastic background in the PrimEx experiment at the Jefferson Laboratory. �� 2007 American Institute of Physics.

Heavy-light mesons scattering from nucleons: Quark-gluon and meson exchanges

We investigate the scattering of heavy-light K and D mesons by nucleons at low energies. The short-distance part of the interaction is described by quark-gluon interchange and the longdistance part is described by a one-meson-exchange model that includes the contributions of vector (��, ��) and scalar (��) mesons. The microscopic quark model incorporates a confining Coulomb potential extracted from lattice QCD simulations and a transverse hyperfine interaction consistent with a finite gluon propagator in the infrared. The derived effective meson-nucleon potential is used in a Lippmann-Schwinger equation to obtain s-wave phase shifts. Our final aim is to set up a theoretical framework that can be extended to finite temperatures and baryon densities. �� 2010 American Institute of Physics.