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1. Incoherent diffractive dijet production and gluon Bose enhancement in the nuclear wave function

   https://doi.org/10.1007/JHEP07(2024)134  

   Kar, Tiyasa; Kovner, Alexander; Li, Ming; Skokov, Vladimir V (July 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We investigate the effect of gluon Bose enhancement in the nuclear wave function on the dijet production in incoherent diffractive processes in DIS and ultraperipheral collisions. We demonstrate that Bose enhancement leads to an enhancement of diffractive dijet production cross section when the transverse momenta of the two jets are aligned at zero relative angle. This enhancement is maximal when the magnitude of the transverse momenta of the two jets are equal, and disappears rather quickly as a function of the ratio of the two momenta. We study both the dilute limit and fully nonlinear dense regime where the nuclear wave function is evolved with the leading order JIMWLK equation. In both cases we observe a visible effect, with it being enhanced by the evolution due to the dynamical generation of the color neutralization scale. 

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2. Direct quarkonium production in DIS from a joint CGC and NRQCD framework

   https://doi.org/10.1103/PhysRevD.110.094039  

   Cheung, Vincent; Kang, Zhong-Bo; Salazar, Farid; Vogt, Ramona (November 2024, Physical Review D)

   We compute the differential cross section for direct quarkonium production in high-energy electron-nucleus collisions at small $x$. Our computation is performed within the nonrelativistic QCD factorization formalism that separates the calculation into short distance coefficients and long distance matrix elements that depend on the color and spin of the state. We obtain the short distance coefficients of the production of the heavy quark pair within the framework of the color glass condensate effective field theory, which resums coherent multiple interactions of the heavy quark pair with the nucleus to all orders. Our results are expressed as the convolution of perturbatively calculable functions with multipoint lightlike Wilson line correlators. In the correlation limit, we establish the correspondence between our color glass condensate formulation with calculations employing the transverse momentum dependent (TMD) framework. We extend this correspondence by resumming kinematic power corrections within the improved TMD framework, which interpolates between the TMD formalism and $k_{\perp }$-factorization formalism. We present a detailed numerical analysis, focusing on $J/\psi$production in the kinematics accessible at the future Electron-Ion Collider, highlighting the importance of genuine higher-order saturation contributions when the electron collides with a large nucleus. Our results are also valid in the photoproduction limit where we expect the largest contribution from genuine higher-order saturation contributions which could be accessed in ultraperipheral collisions of relativistic heavy ions. Published by the American Physical Society2024 

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3. Subleading power corrections to heavy quarkonium production in QCD factorization approach

   https://doi.org/10.1051/epjconf/202227404005  

   Lee, Kyle; Qiu, Jian-Wei; Sterman, George; Watanabe, Kazuhiro (January 2022, EPJ Web of Conferences)

   Rothkopf, A.; Brambilla, N.; Tolos, L.; Tranberg, A.; Kurkela, A.; Roehrich, D.; Andersen, J.O.; Tywoniuk, K.; Antonov, D.; Greensite, J. (Ed.)

   We report the current understanding of heavy quarkonium production at high transverse momentum ( p T ) in hadronic collisions in terms of QCD factorization. In this presentation, we highlight the role of subleading power corrections to heavy quarkonium production, which are essential to describe the p T spectrum of quarkonium at a relatively lower p T . We also introduce prescription to match QCD factorization to fixed-order NRQCD factorization calculations for quarkonium production at low p T . 

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4. Quenching and the UVJ Diagram in the SIMBA Cosmological Simulation

   https://doi.org/10.3847/1538-4357/ac5d3a  

   Akins, Hollis B.; Narayanan, Desika; Whitaker, Katherine E.; Davé, Romeel; Lower, Sidney; Bezanson, Rachel; Feldmann, Robert; Kriek, Mariska (April 2022, The Astrophysical Journal)

   Abstract Over the past decade, rest-frame color–color diagrams have become popular tools for selecting quiescent galaxies at high redshift, breaking the color degeneracy between quiescent and dust-reddened star-forming galaxies. In this work, we study one such color–color selection tool—the rest-frameU−VversusV−Jdiagram—by employing mock observations of cosmological galaxy formation simulations. In particular, we conduct numerical experiments assessing both trends in galaxy properties inUVJspace and the color–color evolution of massive galaxies as they quench at redshiftsz∼ 1–2. We find that our models broadly reproduce the observedUVJdiagram atz= 1–2, including (for the first time in a cosmological simulation) reproducing the population of extremely dust-reddened galaxies in the top right of theUVJdiagram. However, our models primarily populate this region with low-mass galaxies and do not produce as clear a bimodality between star-forming and quiescent galaxies as is seen in observations. The former issue is due to an excess of dust in low-mass galaxies and relatively gray attenuation curves in high-mass galaxies, while the latter is due to the overpopulation of the green valley insimba. When investigating the time evolution of galaxies on theUVJdiagram, we find that the quenching pathway on theUVJdiagram is independent of the quenching timescale, and instead dependent primarily on the average specific star formation rate in the 1 Gyr prior to the onset of quenching. Our results support the interpretation of different quenching pathways as corresponding to the divergent evolution of post-starburst and green valley galaxies. 

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5. Power expansion for heavy quarkonium production at next-to-leading order in e+e− annihilation

   https://doi.org/10.1007/JHEP09(2020)046  

   Lee, Kyle; Sterman, George (September 2020, Journal of High Energy Physics)

   null (Ed.)

   A bstract We study heavy quarkonium production associated with gluons in e + e − annihilation as an illustration of the perturbative QCD (pQCD) factorization approach, which incorporates the first nonleading power in the energy of the produced heavy quark pair. We show how the renormalization of the four-quark operators that define the heavy quark pair fragmentation functions using dimensional regularization induces “evanescent” operators that are absent in four dimensions. We derive closed forms for short-distance coefficients for quark pair production to next-to-leading order ( $$ {\alpha}_s^2 $$ α s 2 ) in the relevant color singlet and octet channels. Using non-relativistic QCD (NRQCD) to calculate the heavy quark pair fragmentation functions up to v 4 in the velocity expansion, we derive analytical results for the differential energy fraction distribution of the heavy quarkonium. Calculations for $$ {}^3{S}_1^{\left[1\right]} $$ 3 S 1 1 and $$ {}^1{S}_0^{\left[8\right]} $$ 1 S 0 8 channels agree with analogous NRQCD analytical results available in the literature, while several color-octet calculations of energy fraction distributions are new. We show that the remaining corrections due to the heavy quark mass fall off rapidly in the energy of the produced state. To explore the importance of evolution at energies much larger than the mass of the heavy quark, we solve the renormalization group equation perturbatively to two-loop order for the $$ {}^1{S}_0^{\left[8\right]} $$ 1 S 0 8 case. 

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