相关论文: Novel azimuthal observables from two-photon collis…
Azimuthal asymmetries in semi-inclusive production of positive (h^+) and negative hadrons (h^-) have been measured by scattering 160 GeV muons off longitudinally polarised deuterons at CERN. The asymmetries were decomposed in several terms…
Recently, significant enhancements of $e^{+} e^{-}$ pair production at very low transverse momentum ($p_{T} < 0.15$ GeV/c) were observed by the STAR collaboration in peripheral hadronic A+A collisions. This excesses can not be described by…
Search for azimuthal asymmetries in semi-inclusive production of charged hadrons by 160 GeV muons on the longitudinally polarized deuterium target, has been performed using the 2002- 2004 COMPASS data. The observed asymmetries integrated…
We study the azimuthal $\cos \varphi$ and $\cos 2\varphi$ asymmetries in heavy-quark pair leptoproduction, $lN\rightarrow l^{\prime}Q\bar{Q}X$, as probes of linearly polarized gluons inside unpolarized proton, where the azimuth $\varphi$ is…
The ALICE Collaboration reports three measurements in ultra-peripheral proton$-$lead collisions at forward rapidity. The exclusive two-photon process \ggmm and the exclusive photoproduction of J/$\psi$ are studied. J/$\psi$ photoproduction…
We show that a sizeable azimuthal asymmetry, characterized by a coefficient v_2, is to be expected for direct photons produced in non-central high energy nuclear collisions. This signal is generated by photons radiated by jets interacting…
Recent experimental results from RHIC and LHC on hard photon emission rates in heavy-ion collisions indicate a large azimuthal asymmetry of photon emission rate parameterized by the elliptic flow v_2. Motivated by a recent proposal that the…
Azimuthal modulations in lepton and heavy-quark pair production in ultraperipheral collisions (UPCs) of highly charged ions are investigated. The modulations in the azimuthal angles of the sum and difference of the transverse momenta of the…
Exclusive hadron production processes in photon-photon collisions provide important tests of QCD at the amplitude level, particularly as measures of hadron distribution amplitudes and skewed parton distributions. The determination of the…
We report a measurement of the differential cross section of $\pi^0$ pair production in single-tag two-photon collisions, $\gamma^* \gamma \to \pi^0 \pi^0$, in $e^+ e^-$ scattering. The cross section is measured for $Q^2$ up to 30 GeV$^2$,…
The Collins effect connects transverse quark spin with a measurable azimuthal dependence in the yield of hadronic fragments around the quark's momentum vector. Using two different reconstruction methods we observe statistically significant…
We present the complete structure of the azimuthal dependences and polarization observables for two-hadron production in $e^+e^-$ annihilation processes within a transverse momentum dependent (TMD) approach adopting the helicity formalism.…
We calculate azimuthal asymmetries in back-to-back production of $J/\psi$ and a photon in electron-proton scattering process at the future electron-ion collider (EIC) using TMD factorization framework. We consider the cases where the proton…
We present an extraction of azimuthal correlations between two pairs of charged pions detected in opposite jets from electron-positron annihilation. These correlations may arise from the dependence of the di-pion fragmentation on the…
Recently HERMES has observed an azimuthal asymmetry in electro-production of neutral pions in semi-inclusive deep-inelastic scattering of unpolarized positrons off longitudinally polarized protons. This asymmetry (like those observed in the…
We propose a novel method to probe light-quark dipole moments by examining the azimuthal asymmetries between a collinear pair of hadrons in semi-inclusive deep inelastic lepton scattering off an unpolarized proton target at the Electron-Ion…
The ALICE Collaboration at the LHC has measured the J/$\psi$ and $\psi^{'}$ photoproduction at mid-rapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. The charmonium is identified via its leptonic decay for events…
The feasibility of observing true tauonium, the bound state of two tau leptons, $\mathcal{T}_0\equiv(\tau^+\tau^-)_0$, via photon-photon collisions at $e^+e^-$ colliders and at the LHC, is studied. The production cross sections of the…
The helicity-dependent single $\pi^{0}$ photoproduction cross section on the deuteron and the angular dependence of the double polarisation observable $E$ for the quasi-free single $\pi^0$ production off the proton and the neutron have been…
Polarisation asymmetries are measured for the hard exclusive leptoproduction of real photons from a longitudinally polarised hydrogen target. These asymmetries arise from the deeply virtual Compton scattering and Bethe-Heitler processes.…