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Search Results: 1 - 10 of 6669 matches for " Alessandro Bacchetta "
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Models for transverse-momentum distributions and transversity
Alessandro Bacchetta
Physics , 2011,
Abstract: I present a short review of models for transverse-momentum distributions and transversity, with a particular attention on general features common to many models. I compare some model results with experimental extractions. I discuss the existence of relations between different functions, their limits of validity, their possible use.
Constraining quark angular momentum through semi-inclusive measurements
Alessandro Bacchetta,Marco Radici
Physics , 2011, DOI: 10.1103/PhysRevLett.107.212001
Abstract: The determination of quark angular momentum requires the knowledge of the generalized parton distribution E in the forward limit. We assume a connection between this function and the Sivers transverse-momentum distribution, based on model calculations and theoretical considerations. Using this assumption, we show that it is possible to fit at the same time nucleon magnetic moments and semi-inclusive single-spin asymmetries. This imposes additional constraints on the Sivers function and opens a plausible way to quantifying quark angular momentum.
Dihadron interference fragmentation functions in proton-proton collisions
Alessandro Bacchetta,Marco Radici
Physics , 2004, DOI: 10.1103/PhysRevD.70.094032
Abstract: We study the production of hadron pairs in proton-proton collisions, selecting pairs with large total transverse momentum with respect to the beam, and small relative transverse momentum, i.e., belonging to a single jet with large transverse momentum. We describe the process in terms of dihadron fragmentation functions. We consider the production of one pair in polarized collisions (with one transversely polarized proton) and the production of two pairs in unpolarized collisions. In the first case, we discuss how to observe the quark transversity distribution in connection with a specific class of dihadron fragmentation functions, named interference fragmentation functions. In the second case, we suggest how to determine the latter and also how to observe linearly polarized gluons.
Quark angular momentum and the Sivers asymmetry
Alessandro Bacchetta,Marco Radici
Physics , 2012,
Abstract: The determination of quark angular momentum requires the knowledge of the generalized parton distribution $E$ in the forward limit. We assume a connection between this function and the Sivers transverse-momentum distribution, based on model calculations and theoretical considerations. Using this assumption, we show that it is possible to fit at the same time nucleon anomalous magnetic moments and semi-inclusive single-spin asymmetries. This imposes additional constraints on the Sivers function and opens a plausible way to quantifying the quark angular momentum.
Evolution of the helicity and transversity Transverse-Momentum-Dependent parton distributions
Alessandro Bacchetta,Alexei Prokudin
Physics , 2013, DOI: 10.1016/j.nuclphysb.2013.07.013
Abstract: We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.
Evolution equations for extended dihadron fragmentation functions
Ceccopieri, Federico A.;Radici, Marco;Bacchetta, Alessandro
High Energy Physics - Phenomenology , 2007, DOI: 10.1016/j.physletb.2007.04.065
Abstract: We consider dihadron fragmentation functions, describing the fragmentation of a parton in two unpolarized hadrons, and in particular extended dihadron fragmentation functions, explicitly dependent on the invariant mass, $M_h$, of the hadron pair. We first rederive the known results on $M_h$-integrated functions using Jet Calculus techniques, and then we present the evolution equations for extended dihadron fragmentation functions. Our results are relevant for the analysis of experimental measurements of two-particle-inclusive processes at different energies.
Dihadron Fragmentation Functions and Transversity
Marco Radici,A. Courtoy,Alessandro Bacchetta
Physics , 2014, DOI: 10.1051/epjconf/20158502025
Abstract: We present preliminary results for an updated extraction of the transversity parton distribution based on the analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets in collinear factorization. Data for proton and deuteron targets by HERMES and COMPASS allow for a flavor separation of the valence components of transversity, while di-hadron fragmentation functions are taken from the semi-inclusive production of two pion pairs in back-to-back jets in $e^+ e^-$ annihilation. The latter data from Belle have been reanalyzed using the replica method and a more realistic estimate of the uncertainties on the chiral-odd interference fragmentation function has been obtained. After encoding this piece of information into the deep-inelastic scattering cross section, the transversity has been re-extracted by using the most recent and more precise COMPASS data for proton target. This picture represents the current most realistic estimate of the uncertainties on our knowledge of transversity. The preliminary results indicate that the valence up component seems smaller and with a narrower error band than in previous extraction.
First extraction of valence transversities in a collinear framework
Alessandro Bacchetta,A. Courtoy,Marco Radici
Physics , 2012, DOI: 10.1007/JHEP03(2013)119
Abstract: We present an extraction of the valence transversity parton distributions based on an analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets. Recently released data for proton and deuteron targets at HERMES and COMPASS permit a flavor separation of valence transversities. The present extraction is performed in the framework of collinear factorization, where dihadron fragmentation functions are involved. The latter are taken from a previous analysis of electron-positron annihilation measurements.
Production of two hadrons in semi-inclusive Deep Inelatic Scattering
Stephen Gliske,Alessandro Bacchetta,Marco Radici
Physics , 2014, DOI: 10.1103/PhysRevD.90.114027
Abstract: We present the general expression, in terms of structure functions, of the cross section for the production of two hadrons in semi-inclusive deep-inelastic scattering. We analyze this process including full transverse-momentum dependence up to subleading twist and check, where possible, the consistency with existing literature.
First glances at the transversity parton distribution through dihadron fragmentation functions
Alessandro Bacchetta,A. Courtoy,Marco Radici
Physics , 2011, DOI: 10.1103/PhysRevLett.107.012001
Abstract: We present first observations of the transversity parton distribution based on an analysis of pion-pair production in deep inelastic scattering off transversely polarized targets. The extraction of transversity relies on the knowledge of dihadron fragmentation functions, which we take from electron-positron annihilation measurements. This is the first attempt to determine the transversity distribution in the framework of collinear factorization.
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