Search results for "distribution function"
showing 10 items of 348 documents
Confronting current NLO parton fragmentation functions with inclusive charged-particle spectra at hadron colliders
2013
The inclusive spectra of charged particles measured at high transverse momenta ($p_T\gtrsim$2GeV/c) in proton-proton and proton-antiproton collisions in the range of center-of-mass energies $\sqrt{s}=200-7000$GeV are compared with next-to-leading order perturbative QCD calculations using seven recent sets of parton-to-hadron fragmentation functions (FFs). Accounting for the uncertainties in the scale choices and in the parton distribution functions, we find that most of the theoretical predictions tend to overpredict the measured LHC and Tevatron cross sections by up to a factor of two. We identify the currently too-hard gluon-to-hadron FFs as the probable source of the problem, and justify…
Double parton correlations and constituent quark models: a light front approach to the valence sector
2014
An explicit evaluation of the double parton distribution functions (dPDFs), within a relativistic Light-Front approach to constituent quark models, is presented. dPDFs encode information on the correlations between two partons inside a target and represent the non-perturbative QCD ingredient for the description of double parton scattering in proton-proton collisions, a crucial issue in the search of new Physics at the LHC. Valence dPDFs are evaluated at the low scale of the model and the perturbative scale of the experiments is reached by means of QCD evolution. The present results show that the strong correlation effects present at the scale of the model are still sizable, in the valence r…
Probing the small- x nuclear gluon distributions with isolated photons at forward rapidities in p+Pb collisions at the LHC
2014
Inclusive direct photon production in p+Pb collisions at the LHC is studied within the NLO perturbative QCD. Our aim is to quantify the dominant $x$ regions probed at different rapidities and to identify the best conditions for testing the nuclear gluon parton distribution functions (nPDFs) at small $x$. A comparison to the inclusive pion production reveals that from these two processes the photons carry more sensitivity to the small-$x$ partons and that this sensitivity can be further increased by imposing an isolation cut for the photon events. The details of the isolation criteria, however, seem to make only a small difference to the studied $x$ sensitivity and have practically no effect…
A model calculation of double parton distribution functions of the pion
2018
Two-parton correlations in the pion are investigated in terms of double parton distribution functions. A Poincar\'e covariant Light-Front framework has been adopted. As non perturbative input, the pion wave function obtained within the so-called soft-wall AdS/QCD model has been used. Results show how novel dynamical information on the structure of the pion, not accessible through one-body parton distribution, are encoded in double parton distribution functions.
DeepXS: fast approximation of MSSM electroweak cross sections at NLO
2018
We present a deep learning solution to the prediction of particle production cross sections over a complicated, high-dimensional parameter space. We demonstrate the applicability by providing state-of-the-art predictions for the production of charginos and neutralinos at the Large Hadron Collider (LHC) at the next-to-leading order in the phenomenological MSSM-19 and explicitly demonstrate the performance for $pp\to\tilde{\chi}^+_1\tilde{\chi}^-_1,$ $\tilde{\chi}^0_2\tilde{\chi}^0_2$ and $\tilde{\chi}^0_2\tilde{\chi}^\pm_1$ as a proof of concept which will be extended to all SUSY electroweak pairs. We obtain errors that are lower than the uncertainty from scale and parton distribution functi…
Rosenbluth Separation of the π^{0} Electroproduction Cross Section.
2016
We present deeply virtual $\pi^0$ electroproduction cross-section measurements at $x_B$=0.36 and three different $Q^2$--values ranging from 1.5 to 2 GeV$^2$, obtained from experiment E07-007 that ran in the Hall A at Jefferson Lab. The Rosenbluth technique was used to separate the longitudinal and transverse responses. Results demonstrate that the cross section is dominated by its transverse component, and thus is far from the asymptotic limit predicted by perturbative Quantum Chromodynamics. An indication of a non-zero longitudinal contribution is provided by the interference term $\sigma_{LT}$ also measured. Results are compared with several models based on the leading twist approach of G…
Density distributions in the $B$ meson
2016
We report on a two-flavor lattice QCD study of the axial, charge and matter distributions of the $B$ meson and its first radial excitation. As our framework is the static limit of Heavy Quark Effective Theory (HQET), taking their Fourier transform gives access to several form factors at the kinematical point $q^2=0$. Moreover they provide some useful information on the nature of an excited state, i.e. a radial excitation of a quark-antiquark bound state or a multihadron state.
Transportation-cost inequality on path spaces with uniform distance
2008
Abstract Let M be a complete Riemannian manifold and μ the distribution of the diffusion process generated by 1 2 ( Δ + Z ) where Z is a C 1 -vector field. When Ric − ∇ Z is bounded below and Z has, for instance, linear growth, the transportation-cost inequality with respect to the uniform distance is established for μ on the path space over M . A simple example is given to show the optimality of the condition.
Dipolar Glass-Like Perovskite Sr0.8Bi0.2TiO3Ceramic
2010
In this work lead-free Sr0.8Bi0.2TiO3 ceramic have been investigated in the frequency range from 20 Hz to 36 GHz. The obtained results show pronounced dispersion below room temperature. It looks more similar to the one observed in dipolar glasses as in relaxors. Calculated relaxation time distribution function broadens towards longest relaxation times with decreasing temperature. The obtained most probable relaxation time fulfills Vogel-Fulcher relationship with the following parameters: dipole activation energy EA/kB = 1718 K, freezing temperature T0 = 65 K, attempt relaxation time, referring to dipole relaxation at very high temperatures, τ0 = 5.5·10−14 s.
Distribution of the relaxation times of the new relaxor 0.4PSN–0.3PMN–0.3PZN ceramics
2005
Abstract The real distribution function of the relaxation times g ( τ ) of the relaxor ferroelectric ceramics 0.4PSN–0.3PMN–0.3PZN is calculated from the experimental dielectric spectra obtained in the frequency range from 20 Hz to 1.25 GHz. Below the Burns temperature T B ≅ 380 K, where the clusters begin to appear on cooling, the distribution of the relaxation times is symmetrically shaped. On cooling, the permittivity and loss spectra strongly broaden and slow down. The g ( τ ) function becomes asymmetrically shaped and the second maximum appears. The width of the g ( τ ) function is calculated at different temperatures. The shortest relaxation time is of the order of 10 −12 s and it r…