Search results for "MESONS"
showing 10 items of 131 documents
Scattering off the color glass condensate
2015
In this thesis the Color Glass Condensate (CGC) framework, which describes quantum chromodynamics (QCD) at high energy, is applied to various scat- tering processes. Higher order corrections to the CGC evolution equations, known as the BK and JIMWLK equations, are also considered. It is shown that the leading order CGC calculations describe the experimen- tal data from electron-proton deep inelastic scattering (DIS), proton-proton and proton-nucleus collisions. The initial condition for the BK evolution equation is obtained by performing a fit to deep inelastic scattering data. The fit result is used as an input to calculations of single particle spectra and nuclear suppression in proton-prot…
Measurement of the lifetime difference in the B$_s^0$ system
2005
We present a study of the decay B_s^0 -> J/psi phi We obtain the CP-odd fraction in the final state at time zero, R_perp = 0.16 +/- 0.10 (stat) +/- 0.02 (syst), the average lifetime of the (B_s, B_sbar) system, tau (B_s^0) =1.39^{+0.13}_{-0.16} (stat) ^{+0.01}_{-0.02} (syst) ps, and the relative width difference between the heavy and light mass eigenstates, Delta Gamma/Gamma = (Gamma_L - Gamma_H)/Gamma =0.24^{+0.28}_{-0.38} (stat) ^{+0.03}_{-0.04} (syst). With the additional constraint from the world average of the B_s^0$lifetime measurements using semileptonic decays, we find tau (B_s^0)= 1.39 +/- 0.06 ~ps and Delta Gamma/\Gamma = 0.25^{+0.14}_{-0.15}. For the ratio of the B_s^0 and B^0 li…
The Isgur-Wise function from the lattice
1995
We calculate the Isgur-Wise function by measuring the elastic scattering amplitude of a $D$ meson in the quenched approximation on a $24^3\times48$ lattice at $\beta=6.2$, using an $O(a)$-improved fermion action. Fitting the resulting chirally-extrapolated Isgur-Wise function to Stech's relativistic-oscillator parametrization, we obtain a slope parameter $\rho^2=1.2+7-3. We then use this result, in conjunction with heavy-quark symmetry, to extract $V_{cb}$\ from the experimentally measured $\bar B\to D^*l\bar\nu\,$\ differential decay width. We find $|V_{cb}|\sqrt{\tau_B/1.48{\mathrm ps}}= 0.038 +2-2 +8-3, where the first set of errors is due to experimental uncertainties, while the second …
A measurement of the K-S lifetime
2002
A measurement of the K_S lifetime is presented using data recorded by the NA48 experiment at the CERN-SPS during 1998 and 1999. The K_S lifetime is derived from the ratio of decay time distributions in simultaneous, collinear K_S and K_L beams, giving a result which is approximately independent of the detector acceptance and with reduced systematic errors. The result obtained is tau_S=(0.89598 +- 0.00048 +- 0.00051)x10^(-10) s, where the first error is statistical and the second systematic.
Interaction of hadrons and tests for the nature of resonances
2016
El propósito de esta Tesis es contribuir al extenso esfuerzo que se ha hecho, en las ultimas décadas, a fin de entender la estructura de las partículas hadrónicas, uno de los temas más importantes en física hadrónica. En los años 50, el desarrollo de los aceleradores de partículas reveló la existencia de una gran cantidad de nuevas resonancias. La proliferación de partículas, poco después, manifestó un patrón, y un esquema de organización para describirlo se hizo necesario. Al principio, se encontró una solución generalizando el concepto de isospín con el modelo de Fermi-Yang de 1959, en el que el protón y el neutrón aparecen como bloques fundamentales y las otras partículas como sus combin…
D-meson production in p-Pb collisions at √sNN = 5.02 TeV and in pp collisions at √s = 7 TeV
2016
Background: In the context of the investigation of the quark gluon plasma produced in heavy-ion collisions, hadrons containing heavy (charm or beauty) quarks play a special role for the characterization of the hot and dense medium created in the interaction. The measurement of the production of charm and beauty hadrons in proton– proton collisions, besides providing the necessary reference for the studies in heavy-ion reactions, constitutes an important test of perturbative quantum chromodynamics (pQCD) calculations. Heavy-flavor production in proton–nucleus collisions is sensitive to the various effects related to the presence of nuclei in the colliding system, commonly denoted cold-nuclea…
Rosenbluth separation of the $\pi^0$ Electroproduction Cross Section off the Neutron
2017
We report the first longitudinal/transverse separation of the deeply virtual exclusive $\pi^0$ electroproduction cross section off the neutron and coherent deuteron. The corresponding four structure functions $d\sigma_L/dt$, $d\sigma_T/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{TT}/dt$ are extracted as a function of the momentum transfer to the recoil system at $Q^2$=1.75 GeV$^2$ and $x_B$=0.36. The $ed \to ed\pi^0$ cross sections are found compatible with the small values expected from theoretical models. The $en \to en\pi^0$ cross sections show a dominance from the response to transversely polarized photons, and are in good agreement with calculations based on the transversity GPDs of the nucle…
Centrality dependence of ψ(2S) suppression in p-Pb collisions at √sNN = 5.02 TeV
2016
The inclusive production of the ψ(2S) charmonium state was studied as a function of centrality in p-Pb collisions at the nucleon-nucleon center of mass energy √ sNN = 5.02 TeV at the CERN LHC. The measurement was performed with the ALICE detector in the center of mass rapidity ranges −4.46 < ycms < −2.96 and 2.03 < ycms < 3.53, down to zero transverse momentum, by reconstructing the ψ(2S) decay to a muon pair. The ψ(2S) production cross section σψ(2S) is presented as a function of the collision centrality, which is estimated through the energy deposited in forward rapidity calorimeters. The relative strength of nuclear effects on the ψ(2S) and on the corresponding 1S charmonium state J/ψ is…
ϕ-Meson production at forward rapidity in p–Pb collisions at √sNN = 5.02 TeV and in pp collisions at √s = 2.76 TeV
2017
The first study of φ-meson production in p–Pb collisions at forward and backward rapidity, at a nucleon– nucleon centre-of-mass energy √sNN = 5.02 TeV, has been performed with the ALICE apparatus at the LHC. The φ-mesons have been identified in the dimuon decay channel in the transverse momentum (pT) range 1 < pT < 7 GeV/c, both in the p-going (2.03 < y < 3.53) and the Pb-going (−4.46 < y < −2.96) directions — where y stands for the rapidity in the nucleon–nucleon centre-of-mass — the integrated luminosity amounting to 5.01 ± 0.19 nb−1 and 5.81 ± 0.20 nb−1, respectively, for the two data samples. Differential cross sections as a function of transverse momentum and rapidity are presented. Th…
Production of K∗ (892) 0 and ϕ(1020) in p–Pb collisions at √sNN = 5.02 TeV
2016
The production of K∗(892)0 and ϕ(1020) mesons has been measured in p–Pb collisions at √sNN = 5.02 TeV. K∗0 and ϕ are reconstructed via their decay into charged hadrons with the ALICE detector in the rapidity range −0.5<y<0. The transverse momentum spectra, measured as a function of the multiplicity, have a pT range from 0 to 15 GeV/c for K∗0 and from 0.3 to 21 GeV/c for ϕ. Integrated yields, mean transverse momenta and particle ratios are reported and compared with results in pp collisions at s√ = 7 TeV and Pb–Pb collisions at √sNN = 2.76 TeV. In Pb–Pb and p–Pb collisions, K∗0 and ϕ probe the hadronic phase of the system and contribute to the study of particle formation mechanisms by compar…