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Open Access Publications from the University of California

Scholarly Works (22 results)

  • Article
Lawrence Berkeley National Laboratory (2010)

We study the initial and final state interaction effects in the transverse momentum dependent parton distributions in the small-x saturation region. In particular, we discuss the quark distributions in the semi-inclusive deep inelastic scattering, Drell-Yan lepton pair production and dijet-correlation processes in pA collisions. We calculate the quark distributions in the scalar-QED model and then extend to the color glass condensate formalism in QCD. The quark distributions are found universal between the DIS and Drell-Yan processes. On the other hand, the quark distribution from the qq'-->qq' channel contribution to the dijet-correlation process is not universal. However, we find that it can be related to the quark distribution in DIS process by a convolution with the normalized unintegrated gluon distribution in the CGC formalism in the large Nc limit.

    Cover page: Initial and Final State Interaction Effects in Small-x Quark Distributions
    • Article
    • Peer Reviewed
    LBL Publications (2018)
    We investigate the QCD resummation for the Higgs boson plus a high PT jet production with large rapidity separations in proton–proton collisions at the LHC. The relevant Balitsky–Fadin–Kuraev–Lipatov (BFKL) and Sudakov logs are identified and resummed. In particular, we apply recent developments of the transverse momentum dependent factorization formalism in the impact factors, which provides a systematic framework to incorporate both the BFKL and Sudakov resummations.
      Cover page: BFKL and Sudakov resummation in higgs boson plus jet production with large rapidity separation
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      • Peer Reviewed
      LBL Publications (2019)
      In this paper, using the Higgs production in forward rapidity region in proton-nucleus collisions as an example, we demonstrate that we can construct a systematic formalism for the threshold resummation for forward rapidity particle productions in the saturation formalism. The forward threshold jet function, which satisfies the corresponding renormalization group equation, is introduced into the new factorization formula. This calculation can be easily generalized to other processes, such as single forward hadron productions at forward rapidity region, and have important phenomenological implications.
        Cover page: On the threshold resummation in forward pA collisions
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        • Peer Reviewed
        LBL Publications (2014)
        In a recent paper (arXiv:1403.5221), Kang et al.proposed the so-called "rapidity factorization" for the single inclusive forward hadron production in pA collisions. We point out that the leading small-x logarithm was mis-identified in this paper, and hence the newly added next-to-leading order correction term is unjustified and should be absent in view of the small-x factorization.
          Cover page: Comment on "Next-to-leading order forward hadron production in the small-x regime: rapidity factorization" arXiv:1403.5221 by Kang et al
          • Article
          • Peer Reviewed
          LBL Publications (2017)
          We present a full evaluation of the deeply virtual Compton scattering cross section in the dipole framework in the small-x region. The result features the cosφ and cos2φ azimuthal angular correlations, which have been missing in previous studies based on the dipole model. In particular, the cos2φ term is generated by the elliptic gluon Wigner distribution of which the measurement at the planned electron-ion collider provides important information about the gluon tomography at small x. We also show the consistency with the standard collinear factorization approach based on the quark and gluon generalized parton distributions.
            Cover page: Gluon tomography from deeply virtual Compton scattering at small x
            • Article
            • Peer Reviewed
            LBL Publications (2020)
            We investigate the effect of PT-broadening on jet substructure observables in heavy-ion collisions at the LHC. As an example, we focus on the opening angle of the two branches that satisfy the soft drop grooming condition in a highly energetic jet. The medium modification of the angular distribution can provide important information on the jet transport properties of hot QCD matter. In addition, we take into account a change of the overall fraction of quark and gluon jets in heavy-ion collisions. We comment on the comparison to a recent measurement from the ALICE Collaboration.
              Cover page: Can we observe jet P T -broadening in heavy-ion collisions at the LHC?
              • Article
              • Peer Reviewed
              LBL Publications (2020)
              We investigate the azimuthal angular correlation between the lepton transverse momentum P_{⊥} and the impact parameter b_{⊥} in noncentral heavy-ion collisions, where the leptons are produced through two-photon scattering. Among the Fourier harmonic coefficients, a significant v_{4} asymmetry is found for the typical kinematics at RHIC and LHC with a mild dependence on the P_{⊥}, whereas v_{2} is power suppressed by the lepton mass over P_{⊥}. This unique prediction, if confirmed from the experiments, shall provide crucial information on the production mechanism for the dilepton in two-photon processes.
                Cover page: Momentum Anisotropy of Leptons from Two-Photon Processes in Heavy-Ion Collisions
                • Article
                • Peer Reviewed
                LBL Publications (2016)
                We investigate the close connection between the quantum phase space Wigner distribution of small-x gluons and the color dipole scattering amplitude, and we propose studying it experimentally in the hard diffractive dijet production at the planned electron-ion collider. The angular correlation between the nucleon recoiled momentum and the dijet transverse momentum probes the nontrivial correlation in the phase space Wigner distribution. This experimental study not only provides us with three-dimensional tomographic pictures of gluons inside high energy protons-it gives a unique and interesting signal for the small-x dynamics with QCD evolution effects.
                  • Article
                  • Peer Reviewed
                  LBL Publications (2017)
                  We study the transverse momentum dependent (TMD) parton distributions at small-x in a consistent framework that takes into account the TMD evolution and small-x evolution simultaneously. The small-x evolution effects are included by computing the TMDs at appropriate scales in terms of the dipole scattering amplitudes, which obey the relevant Balitsky–Kovchegov equation. Meanwhile, the TMD evolution is obtained by resumming the Collins–Soper type large logarithms emerged from the calculations in small-x formalism into Sudakov factors.
                    Cover page: Transverse momentum dependent parton distributions at small-x
                    • Article
                    • Peer Reviewed
                    LBL Publications (2017)
                    Using deep inelastic scattering on a large nucleus as an example, we consider the transverse momentum broadening of partons in hard processes in the presence of medium. We find that one can factorize the vacuum radiation contribution and medium related PT broadening effects into the Sudakov factor and medium dependent distributions, respectively. Our derivations can be generalized to other hard processes, such as dijet productions, which can be used as a probe to measure the medium PT broadening effects in heavy ion collisions when Sudakov effects are not overwhelming.
                      Cover page: Medium induced transverse momentum broadening in hard processes
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