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1. General mass variable flavor number scheme for $Z$ boson production in association with a heavy quark at hadron colliders

   https://doi.org/10.1103/PhysRevD.110.114030  

   Guzzi, Marco; Nadolsky, Pavel; Reina, Laura; Wackeroth, Doreen; Xie, Keping (December 2024, Physical Review D)

   We present a methodology to streamline implementation of massive-quark radiative contributions in calculations with a variable number of active partons in proton-proton collisions. The methodology introduces and heavy-quark parton distribution functions (PDFs) to implement calculations in the Aivazis–Collins–Olness–Tung (ACOT) factorization scheme and its simplified realization in various processes up to the next-to-the-next-to-leading order in the QCD coupling strength. Interpolation tables for bottom-quark subtraction and residual distributions for CT18 NLO and NNLO PDF ensembles are provided in the common LHAPDF6 format. A numerical calculation of $Z$-boson production with at least one $b$jet at the Large Hadron Collider beyond the lowest order in QCD is considered for illustration purposes. Published by the American Physical Society2024 

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2. Heavy-flavor impact on CTEQ-TEA global QCD analyses

   https://doi.org/10.1051/epjconf/202227000004  

   Guzzi, Marco; Ablat, Alim; Dulat, Sayipjamal; Hou, Tie-Jiun; Nadolsky, Pavel; Sitiwaldi, Ibrahim; Xie, Keping; Yuan, C.-P. (January 2022, EPJ Web of Conferences)

   Bruno, G.E.; Chiodini, G.; Colangelo, P.; Corianò, C.; Creanza, D.M.; De Fazio, F.; Nappi, E. (Ed.)

   We discuss heavy-flavor production at hadron colliders in recent global QCD analyses to determine parton distribution functions (PDFs) in the proton. We discuss heavy-flavor treatments in precision theory predictions at the LHC. In particular, we discuss factorization schemes in presence of heavy flavors in proton-proton collisions, as well as the impact of heavy-flavor production at the LHC on PDFs. We show results of recent updates beyond CT18, the latest global QCD analysis from the CTEQ-TEA group. 

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3. Search for dark QCD with emerging jets in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP07(2024)142  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; Jeitler, M; et al (July 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> A search for “emerging jets” produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed using data collected by the CMS experiment corresponding to an integrated luminosity of 138 fb⁻¹. This search examines a hypothetical dark quantum chromodynamics (QCD) sector that couples to the standard model (SM) through a scalar mediator. The scalar mediator decays into an SM quark and a dark sector quark. As the dark sector quark showers and hadronizes, it produces long-lived dark mesons that subsequently decay into SM particles, resulting in a jet, known as an emerging jet, with multiple displaced vertices. This search looks for pair production of the scalar mediator at the LHC, which yields events with two SM jets and two emerging jets at leading order. The results are interpreted using two dark sector models with different flavor structures, and exclude mediator masses up to 1950 (1950) GeV for an unflavored (flavor-aligned) dark QCD model. The unflavored results surpass a previous search for emerging jets by setting the most stringent mediator mass exclusion limits to date, while the flavor-aligned results provide the first direct mediator mass exclusion limits to date. 

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4. Bottom Hadrochemistry in High-Energy Hadronic Collisions

   https://doi.org/10.1103/PhysRevLett.131.012301  

   He, Min; Rapp, Ralf (July 2023, Physical Review Letters)

   The hadrochemistry of bottom quarks (b) produced in hadronic collisions encodes valuable information on the mechanism of color neutralization in these reactions. Since the b-quark mass is much larger than the typical hadronic scale of 1 GeV, bbar pair production is expected to be well separated from subsequent hadronization processes. A significantly larger fraction of b baryons has been observed in proton-proton (pp) and proton-antiproton (pbarp) reactions relative to eþe2 collisions, challenging theoretical descriptions. We address this problem by employing a statistical hadronization approach with an augmented set of b-hadron states beyond currently measured ones, guided by the relativistic quark model and lattice-QCD computations. Assuming relative chemical equilibrium between different b-hadron yields, thermal densities are used as fragmentation weights of b quarks into various hadron species. With quark model estimates of the decay patterns of excited states, the fragmentation fractions of weakly decaying b hadrons are computed and found to agree with measurements in pbarp collisions at the Tevatron. By combining transverse-momentum (pT) distributions of b quarks from perturbative QCD with thermal weights and independent fragmentation toward high pT, a fair description of the pT-dependent B-meson ratios measured in pp collisions at the LHC is obtained. The observed enhancement of Lambda_b attributed to the feeddown from thus far unobserved excited b baryons. Finally, we implement the hadrochemistry into a strongly coupled transport approach for b quarks in heavy-ion collisions, utilizing previously determined b-quark transport coefficients in the quark-gluon plasma, to highlight the modifications of hadrochemistry and collective behavior of b hadrons in Pb-Pb collisions at the LHC. 

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5. The Sivers asymmetry in hadronic dijet production

   https://doi.org/10.1007/JHEP02(2021)066  

   Kang, Zhong-Bo; Lee, Kyle; Shao, Ding Yu; Terry, John (February 2021, Journal of High Energy Physics)

   null (Ed.)

   A bstract We study the single spin asymmetry in the back-to-back dijet production in transversely polarized proton-proton collisions. Such an asymmetry is generated by the Sivers functions in the incoming polarized proton. We propose a QCD formalism in terms of the transverse momentum dependent parton distribution functions, which allow us to resum the large logarithms that arise in the perturbative calculations. We make predictions for the Sivers asymmetry of hadronic dijet production at the kinematic region that is relevant to the experiment at the Relativistic Heavy Ion Collider (RHIC). We further compute the spin asymmetries in the selected positive and negative jet charge bins, to separate the contributions from u - and d -quark Sivers functions. We find that both the sign and size of our numerical results are roughly consistent with the preliminary results from the STAR collaboration at the RHIC. 

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