Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Alessandria

We present a phenomenological analysis of the $\mathrm{cos}2\ensuremath{\phi}$ asymmetry recently measured by the COMPASS and HERMES collaborations in unpolarized semi-inclusive deep inelastic scattering. In the kinematical regimes explored by these experiments the asymmetry arises from transverse-spin and intrinsic transverse-momentum effects. We consider the leading-twist contribution, related to the so-called Boer-Mulders transverse-polarization distribution ${h}_{1}^{\ensuremath{\perp}}(x,{k}_{T}^{2})$, and the twist-4 Cahn contribution, involving unpolarized transverse-momentum distribution functions. We show that a reasonably good fit of the preliminary data sets from COMPASS and HERMES is achieved with a Boer-Mulders function consistent with the main theoretical expectations. Our conclusion is that the COMPASS and HERMES measurements represent the first experimental evidence of the Boer-Mulders effect in SIDIS.

We study polarized and unpolarized semi-inclusive deep inelastic scattering processes, $\ensuremath{\ell}({S}_{\ensuremath{\ell}})+p(S)\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{'}}hX$, within a QCD parton model motivated by a generalized QCD factorization scheme. We take into account all transverse motions, of partons inside the initial proton and of hadrons inside the fragmenting partons and use the helicity formalism. The elementary interactions are computed at leading order with noncollinear exact kinematics, which introduces phases in the expressions of their helicity amplitudes. Several transverse momentum dependent distribution and fragmentation functions appear and contribute to the cross sections and to spin asymmetries. Our results agree with those obtained with different formalisms, showing the consistency of our approach. The full expression for single and double spin asymmetries ${A}_{{S}_{\ensuremath{\ell}}S}$ is derived. Simplified, explicit analytical expressions, convenient for phenomenological studies, are obtained assuming a factorized Gaussian dependence on intrinsic momenta for transverse momentum dependent functions.

We study the $\mathrm{cos}2\ensuremath{\phi}$ azimuthal asymmetry in unpolarized semi-inclusive DIS, taking into account both the perturbative contribution (gluon emission and splitting) and the nonperturbative effects arising from intrinsic transverse motion and transverse spin of quarks. In particular we explore the possibility to extract from $⟨\mathrm{cos}2\ensuremath{\phi}⟩$ some information about the Boer-Mulders function ${h}_{1}^{\ensuremath{\perp}}$, which represents a transverse-polarization asymmetry of quarks inside an unpolarized hadron. Predictions are presented for the HERMES, COMPASS and JLab kinematics, where $⟨\mathrm{cos}2\ensuremath{\phi}⟩$ is dominated by the kinematical higher-twist contribution, and turns to be of order of a few percent. We show that under reasonable assumptions a larger asymmetry in ${\ensuremath{\pi}}^{\ensuremath{-}}$ production, compared to ${\ensuremath{\pi}}^{+}$ production, would represent a signature of the Boer-Mulders effect.

Given a Hopf algebra H, we study modules and bimodules over an algebra A that carry an H-action, as well as their morphisms and connections. Bimodules naturally arise when considering noncommutative analogues of tensor bundles. For quasitriangular Hopf algebras and bimodules with an extra quasi-commutativity property we induce connections on the tensor product over A of two bimodules from connections on the individual bimodules. This construction applies to arbitrary connections, i.e. not necessarily Hequivariant ones, and further extends to the tensor algebra generated by a bimodule and its dual. Examples of these noncommutative structures arise in deformation quantization via Drinfeld twists of the commutative differential geometry of a smooth manifold, where the Hopf algebra H is the universal enveloping algebra of vector fields (or a finitely generated Hopf subalgebra).

Using a previous extraction of the quark Boer-Mulders distributions from semi-inclusive deep inelastic scattering data, we fit the unpolarized Drell-Yan data on the $\mathrm{cos}2\ensuremath{\phi}$ asymmetry, determining the antiquark Boer-Mulders distributions. A good agreement with the data is found in the region of low ${q}_{T}$, where the transverse-momentum factorization approach applies.

Taking into account the effect of final-state interaction, we calculate the non-zero (naïve) T-odd transverse momentum dependent distribution h1⊥(x,k⊥2) of the pion in a quark-spectator-antiquark model with effective pion-quark-antiquark coupling as a dipole form factor. Using the model result we estimate the cos2ϕ asymmetries in the unpolarized π−N Drell–Yan process which can be expressed as h1⊥×h¯1⊥. We find that the resulting h1π⊥(x,k⊥2) has the advantage to reproduce the asymmetry that agrees with the experimental data measured by NA10 Collaboration. We estimate the cos2ϕ asymmetries averaged over the kinematics of NA10 experiments for 140, 194 and 286 GeV π− beam and compare them with relevant experimental data.

We develop a general strategy to express noncommutative actions in terms of commutative ones by using a recently developed geometric generalization of the Seiberg-Witten map between noncommutative and commutative fields. We apply this general scheme to the noncommutative vierbein gravity action and provide a Seiberg-Witten differential equation for the action itself as well as a recursive solution at all orders in the noncommutativity parameter $\ensuremath{\theta}$. We thus express the action at order ${\ensuremath{\theta}}^{n+2}$ in terms of noncommutative fields of order at most ${\ensuremath{\theta}}^{n+1}$ and, iterating the procedure, in terms of noncommutative fields of order at most ${\ensuremath{\theta}}^{n}$. This in particular provides the explicit expression of the action at order ${\ensuremath{\theta}}^{2}$ in terms of the usual commutative spin connection and vierbein fields. The result is an extended gravity action on commutative spacetime that is manifestly invariant under local Lorentz rotations and general coordinate transformations.

We present a point-by-point determination of the valence transversity distributions from two different types of processes: single-hadron production and dihadron production, both in semi-inclusive deep inelastic scattering and ${e}^{+}{e}^{\ensuremath{-}}$ annihilation. The extraction is based on some simple assumptions and does not require any parametrization. The transversity distributions obtained from Collins effect in single-hadron production and from interference effects in dihadron production are found to be compatible with each other.

We investigate the origin of the cos2ϕ azimuthal asymmetry in unpolarized semi-inclusive DIS. The contributions to this asymmetry arising from the intrinsic transverse motion of quarks are explicitly evaluated, and predictions for the HERMES and COMPASS kinematic regimes are presented. We show that the effect of the leading-twist Boer–Mulders function h1⊥(x,kT2), which describes a correlation between the transverse momentum and the transverse spin of quarks, is quite significant and may also account for a part of the cos2ϕ asymmetry measured by ZEUS in the perturbative domain.

We present a phenomenological analysis of the $\mathrm{cos}\ensuremath{\phi}$ and $\mathrm{cos}2\ensuremath{\phi}$ asymmetries in unpolarized semi-inclusive deep inelastic scattering, based on the recent multidimensional data released by the COMPASS and HERMES collaborations. In the transverse-momentum-dependent framework, valid at relatively low transverse momenta, these asymmetries arise from intrinsic transverse momentum and transverse spin effects, and from their correlations. The role of the Cahn and Boer-Mulders effects in both azimuthal moments is explored up to order $1/Q$. As the kinematics of the present experiments is dominated by the low-${Q}^{2}$ region, higher-twist contributions turn out to be important, affecting the results of our fits.

We review the $OSp(1|4)$-invariant formulation of $N=1$, $D=4$ supergravity and present its noncommutative extension, based on a $\ensuremath{\star}$ product originating from an Abelian twist with deformation parameter $\ensuremath{\theta}$. After the use of a geometric generalization of the Seiberg-Witten map, we obtain an extended (higher-derivative) supergravity theory, invariant under usual $OSp(1|4)$ gauge transformations. Gauge fixing breaks the $OSp(1|4)$ symmetry to its Lorentz subgroup and yields a Lorentz-invariant extended theory for which the classical limit $\ensuremath{\theta}\ensuremath{\rightarrow}0$ is the usual $N=1$, $D=4$ anti--de Sitter supergravity.

We present next-to-leading order predictions for double transverse-spin asymmetries in Drell–Yan dilepton production initiated by proton–antiproton scattering. The kinematic region of the proposed PAX experiment at GSI: 30≲s≲200GeV2 and 2≲M≲7GeV is examined. The Drell–Yan asymmetries turn out to be large, in the range 20–40%. Measuring these asymmetries would provide the cleanest determination of the quark transversity distributions.

We study the role of large clusters of center vortices in producing confinement in $3\mathrm{D}$ ${Z}_{2}$ gauge theory. First, we modify each configuration of a Monte Carlo--generated ensemble in the confined phase by removing the largest cluster of center vortices, and show that the ensemble thus obtained does not confine. Conversely, we show that by removing all of the small clusters of center vortices and leaving the largest one only, confinement is preserved, albeit with a string tension significantly smaller than the original one. Remarkably, also the string corrections due to the quantum fluctuations of the confining flux tube are preserved by this transformation.

Given a Hopf algebra H and an algebra A that is an H-module algebra we consider the category of left H-modules and A-bimodules [Formula: see text], where morphisms are just right A-linear maps (not necessarily H-equivariant). Given a twist [Formula: see text] of H we then quantize (deform) H to [Formula: see text], A to A ⋆ and correspondingly the category [Formula: see text] to [Formula: see text]. If we consider a quasitriangular Hopf algebra H, a quasi-commutative algebra A and quasi-commutative A-bimodules, we can further construct and study tensor products over A of modules and of morphisms, and their twist quantization. This study leads to the definition of arbitrary (i.e., not necessarily H-equivariant) connections on quasi-commutative A-bimodules, to extend these connections to tensor product modules and to quantize them to A ⋆ -bimodule connections. Their curvatures and those on tensor product modules are also determined.

We prove the discrete triality invariance of the N=2 NSR superstring moving in a D=2+2 target space. We find that triality holds also in the Siegel–Berkovits formulation of the selfdual superstring. A supersymmetric generalization of Cayley's hyperdeterminant, based on a quartic invariant of the SL(2|1)3 superalgebra, is presented.

The possibility to detect thermal neutrons with single gap Resistive Plate Chambers has been investigated. To detect neutrons a 10B4C thin coating on the inner surface of one RPC electrode is used as thermal neutron converter. The RPC detects the charged particles generated by neutrons via the (n, α) reaction on Boron. Tests on converter samples have been performed with a thermalized 252Cf source in order to evaluate the conversion efficiency: a good agreement between experimental results and simulation has been achieved. A detector prototype has been developed and tested on a low energy neutron beam at the European laboratories JRC in Belgium. A detailed description of the detector and the experimental test results are presented.

We continue the analysis of the $D$-deformed Wess-Zumino model that we introduced in M. Dmitrijevic and V. Radovanovic, J. High Energy Phys. 04 (2009) 108. The model is defined by a deformation that is non-Hermitian and given in terms of the covariant derivatives ${D}_{\ensuremath{\alpha}}$. We calculate one-loop divergences in the two-point, three-point, and four-point Green functions. Possibilities to render the model renormalizable are discussed.

ALICE is a general purpose experiment designed to investigate nucleus-nucleus collisions at the CERN Large Hadron Collider (LHC). The Inner Tracking System (ITS) is a key ALICE detector for the study of heavy flavour production in pp and Pb-Pb collisions. Very important and original results have been obtained in the first three years of data taking. After the completion of the approved physics programme, ALICE will focus on precision measurements of the Quark-Gluon Plasma (QGP) properties. This requires improved tracking capabilities and a higher readout rate to exploit the increased luminosity expected to be delivered by LHC in the future. During the second LHC Long Shutdown in 2018 a completely new ITS, based on today's frontier technologies, is planned to be installed. The new detector will greatly improve the current performance in terms of pointing resolution, low transverse momentum resolution, standalone tracking efficiency and fast readout capabilities. The present contribution describes the ongoing developments and the expected physics performance of the new ITS.

Given a Hopf algebra H, we study modules and bimodules over an algebra A that carry an H-action, as well as their morphisms and connections. Bimodules naturally arise when considering noncommutative analogues of tensor bundles. For quasitriangular Hopf algebras and bimodules with an extra quasi-commutativity property we induce connections on the tensor product over A of two bimodules from connections on the individual bimodules. This construction applies to arbitrary connections, i.e. not necessarily H-equivariant ones, and further extends to the tensor algebra generated by a bimodule and its dual. Examples of these noncommutative structures arise in deformation quantization via Drinfeld twists of the commutative differential geometry of a smooth manifold, where the Hopf algebra H is the universal enveloping algebra of vector fields (or a finitely generated Hopf subalgebra). We extend the Drinfeld twist deformation theory of modules and algebras to morphisms and connections that are not necessarily H-equivariant. The theory canonically lifts to the tensor product structure.

We explain precisely what it means to have a connection with torsion as a solution of the Einstein equations. While locally the theory remains the same, the new formulation allows for topologies that would have been excluded in the standard formulation of gravity. In this formulation it is possible to couple arbitrary torsion to gauge fields without breaking the gauge invariance.