4,368 research outputs found

    Black hole solutions of dimensionally reduced Einstein-Gauss-Bonnet gravity with a cosmological constant

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    We study the phase space of the spherically symmetric solutions of the system obtained from the dimensional reduction of the six-dimensional Einstein-Gauss-Bonnet action with a cosmological constant. We show that all the physical solutions have anti-de Sitter asymptotic behavior.Comment: 13 pages, plain Te

    Partonic Transverse Motion in Unpolarized Semi-Inclusive Deep Inelastic Scattering

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    We analyse the role of partonic transverse motion in unpolarized Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes. Imposing appropriate kinematical conditions, we find some constraints which fix an upper limit to the range of allowed kt values and lead to interesting results, particularly for some observables like the azimuthal modulation of the unpolarized SIDIS cross section and the average transverse momentum of the final, detected hadron.Comment: To appear in the Proceedings of the XIX International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2011), April 11-15, 2011, Newport News, VA US

    Transverse single-spin asymmetries in proton-proton collisions at the AFTER@LHC experiment in a TMD factorisation scheme

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    The inclusive large-pTp_T production of a single pion, jet or direct photon, and Drell-Yan processes, are considered for proton-proton collisions in the kinematical range expected for the fixed-target experiment AFTER, proposed at LHC. For all these processes, predictions are given for the transverse single-spin asymmetry, ANA_N, computed according to a Generalised Parton Model previously discussed in the literature and based on TMD factorisation. Comparisons with the results of a collinear twist-3 approach, recently presented, are made and discussed.Comment: RevTex4, 12 pages, 36 eps figures. V2: Few paragraphs and comments added. Several references added. Results unchanged. Matches the published versio

    A general formalism for single and double spin asymmetries in inclusive hadron production

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    We present a calculation of single and double spin asymmetries for inclusive hadron production in hadronic collisions. Our approach is based on Leading Order (LO) perturbative QCD and generalized factorization theorems, with full account of intrinsic parton momentum, k_T, effects. This leads to a new class of spin and k_T-dependent distribution and fragmentation functions. Limiting ourselves to consider leading twist functions, we show how they could play a relevant role in producing non-vanishing spin asymmetries.Comment: LaTeX, 8 pages, uses ws-procs9x6.cls. Talk delivered by S. Melis at the ``X Convegno su Problemi di Fisica Nucleare Teorica'', October 6-9, 2004, Cortona, Ital

    Masses and decay constants of D(s)∗D_{(s)}^* and B(s)∗B_{(s)}^* mesons in Lattice QCD with Nf=2+1+1N_f = 2 + 1 + 1 twisted-mass fermions

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    We present a lattice calculation of the decay constants and masses of D(s)∗D_{(s)}^* and B(s)∗B_{(s)}^* mesons using the gauge configurations produced by the European Twisted Mass Collaboration (ETMC) with Nf=2+1+1N_f = 2 + 1 + 1 dynamical quarks and at three values of the lattice spacing a∼0.06−0.09a \sim 0.06 - 0.09 fm. Pion masses are simulated in the range mπ∼210−450m_{\pi} \sim 210 - 450 MeV, while the strange and charm quark masses are close to their physical values. We computed the ratios of vector to pseudoscalar decay constants or masses for various values of the heavy-quark mass mhm_h in the range 0.7mcphys≲mh≲3mcphys0.7 m_c^{phys} \lesssim m_h \lesssim 3 m_c^{phys}. In order to reach the physical b-quark mass, we exploited the HQET prediction that, in the static limit of infinite heavy-quark mass, all the considered ratios are equal to one. We obtain: fD∗/fD=1.078(36), f_{D^*}/f_{D} = 1.078(36), mD∗/mD=1.0769(79)m_{D^*}/m_{D} = 1.0769(79), fDs∗/fDs=1.087(20)f_{D^*_{s}}/f_{D_{s}} = 1.087(20), mDs∗mDs=1.0751(56)m_{D^*_{s}}m_{D_{s}} = 1.0751(56), fB∗/fB=0.958(22)f_{B^*}/f_{B} = 0.958(22), mB∗/mB=1.0078(15)m_{B^*}/m_{B} = 1.0078(15), fBs∗/fBs=0.974(10)f_{B^*_{s}}/f_{B_{s}} = 0.974(10) and mBs∗/mBs=1.0083(10)m_{B^*_{s}}/m_{B_{s}} = 1.0083(10). Combining them with the corresponding experimental masses from the PDG and the pseudoscalar decay constants calculated by ETMC, we get: fD∗=223.5(8.4) MeVf_{D^*} = 223.5(8.4)~\mathrm{MeV}, mD∗=2013(14) MeVm_{D^*} = 2013(14)~\mathrm{MeV}, fDs∗=268.8(6.6) MeVf_{D^*_{s}} = 268.8(6.6)~\mathrm{MeV}, mDs∗=2116(11) MeV m_{D^*_{s}} = 2116(11)~\mathrm{MeV}, fB∗=185.9(7.2) MeVf_{B^*} = 185.9(7.2)~\mathrm{MeV}, mB∗=5320.5(7.6) MeVm_{B^*} = 5320.5(7.6)~\mathrm{MeV}, fBs∗=223.1(5.4) MeVf_{B^*_{s}} = 223.1(5.4)~\mathrm{MeV} and mBs∗=5411.36(5.3) MeVm_{B^*_{s}}= 5411.36(5.3)~\mathrm{MeV}.Comment: 7 pages, 4 figures, in proceedings of 34th annual International Symposium on Lattice Field Theory, 24-30 July 2016, University of Southampton (UK). In version v2 the quality of the figures is improve

    Phenomenology of Sivers Effect with TMD Evolution

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    Following the TMD evolution scheme recently proposed for the unpolarized and the Sivers distribution function, we propose a simple strategy to take into account this TMD Q^2 dependence in our phenomenological extraction of the Sivers function from SIDIS data. New results are presented and possible future applications are discussed.Comment: Contribution to the Proceedings of the XX International Workshop on Deep-Inelastic Scattering and related subjects (DIS2012), 26-30 March 2012, Bonn, Germany. One figure correcte

    Constraints on Gluon Sivers Distribution from RHIC Results

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    We consider the recent RHIC data on the transverse single spin asymmetry (SSA) A_N, measured in p(transv. polarized) p --> pion X processes at mid-rapidity by the PHENIX Collaboration. We analyze this experimental information within a hard scattering approach based on a generalized QCD factorization scheme, with unintegrated, transverse momentum dependent (TMD), parton distribution and fragmentation functions. In this kinematical region, only the gluon Sivers effect could give a large contribution to A_N; its vanishing value is thus used to give approximate upper limits on the gluon Sivers function (GSF). Additional constraints from the Burkardt sum rule for the Sivers distributions are also discussed.Comment: LaTeX 2e, 4 pages, 2 ps figures, uses aipproc.cls. Talk delivered by U. D'Alesio at the "17th International Spin Physics Symposium", SPIN2006, October 2-7, 2006, Kyoto, Japa
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