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1. Transverse energy-energy correlators in the color-glass condensate at the electron-ion collider

   https://doi.org/10.1103/PhysRevD.109.094012  

   Kang, Zhong-Bo; Penttala, Jani; Zhao, Fanyi; Zhou, Yiyu (May 2024, Physical Review D)

   We investigate the transverse energy-energy correlators (TEEC) in the small- $x$regime at the upcoming Electron-Ion Collider (EIC). Focusing on the back-to-back production of electron-hadron pairs in both $ep$and $eA$collisions, we establish a factorization formula given in terms of the hard function, quark distributions, soft functions, and TEEC jet functions, where the gluon saturation effect is incorporated. Numerical results for TEEC in both $ep$and $eA$collisions are presented, together with the nuclear modification factor $R_A$. Our analysis reveals that TEEC observables in deep inelastic scattering provide a valuable approach for probing gluon saturation phenomena. Our findings underscore the significance of measuring TEEC at the EIC, emphasizing its efficacy in advancing our understanding of gluon saturation and nuclear modifications in high-energy collisions. Published by the American Physical Society2024 

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2. Observation of $t\overline{t}$ Production in Pb+Pb Collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ with the ATLAS Detector

   https://doi.org/10.1103/PhysRevLett.134.142301  

   Aad, G; Aakvaag, E; Abbott, B; Abdelhameed, S; Abeling, K; Abicht, N J; Abidi, S H; Aboelela, M; Aboulhorma, A; Abramowicz, H; et al (April 2025, Physical Review Letters)

   Top-quark pair production is observed in lead–lead ( $\mathrm{Pb}+\mathrm{Pb}$) collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$at the Large Hadron Collider with the ATLAS detector. The data sample was recorded in 2015 and 2018, amounting to an integrated luminosity of $1.9{\mathrm{nb}}^{-1}$. Events with exactly one electron and one muon and at least two jets are selected. Top-quark pair production is measured with an observed (expected) significance of 5.0 (4.1) standard deviations. The measured top-quark pair production cross section is ${\sigma }_{t\overline{t}}=3.6{}_{-0.9}^{+1.0}\left(\mathrm{stat}\right){}_{-0.5}^{+0.8}\left(\mathrm{syst}\right)\mathrm{\mu }\mathrm{b}$, with a total relative uncertainty of 31%, and is consistent with theoretical predictions using a range of different nuclear parton distribution functions. The observation of this process consolidates the evidence of the existence of all quark flavors in the preequilibrium stage of the quark-gluon plasma at very high energy densities, similar to the conditions present in the early Universe. © 2025 CERN, for the ATLAS Collaboration2025CERN 

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3. One-jettiness DIS event shape at ${\mathrm{N}}^3\mathrm{LL}+\mathcal{O}\left({\alpha }_s^2\right)$

   https://doi.org/10.1103/PhysRevD.110.014045  

   Cao, Haotian; Kang, Zhong-Bo; Liu, Xiaohui; Mantry, Sonny (July 2024, Physical Review D)

   We present results for the ${\tau }_1$and ${\tau }_{1a}$1-jettiness global event shape distributions, for deep inelastic scattering (DIS), at the ${\mathrm{N}}^3\mathrm{LL}+\mathcal{O}\left({\alpha }_s^2\right)$level of accuracy. These event-shape distributions quantify and characterize the pattern of final state radiation in electron-nucleus collisions. They can be used as a probe of nuclear structure functions, as nuclear medium effects in jet production, and for a precision extraction of the QCD strong coupling. The results presented here, along with the corresponding numerical codes, can be used for analyses with HERA data, in Electron-Ion Collider (EIC) simulation studies, and for eventual comparison with real EIC data. Published by the American Physical Society2024 

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4. Up and down quark structure of the proton

   https://doi.org/10.1103/PhysRevD.110.L091101  

   Abazov, V M; Abbott, B; Acharya, B S; Adams, M; Adams, T; Agnew, J P; Alexeev, G D; Alkhazov, G; Alton, A; Askew, A; et al (November 2024, Physical Review D)

   We report an improved measurement of the valence $u$and $d$quark distributions from the forward-backward asymmetry in the Drell-Yan process using $8.6{\mathrm{fb}}^{-1}$of data collected with the D0 detector in $p\overline{p}$collisions at $\sqrt{s}=1.96$. This analysis provides the values of new structure parameters that are directly related to the valence up and down quark distributions in the proton. In other experimental results measuring the quark content of the proton, $d$quark contributions are mixed with those from other quark flavors. In this measurement, the $u$and $d$quark contributions are separately extracted by applying a factorization of the QCD and electroweak portions of the forward-backward asymmetry. Published by the American Physical Society2024 

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5. Transverse energy-energy correlator for vector boson-tagged hadron production in $pp$ and $pA$ collisions

   https://doi.org/10.1103/1djw-8zrh  

   Kang, Zhong-Bo; Lee, Sookhyun; Penttala, Jani; Zhao, Fanyi; Zhou, Yiyu (July 2025, Physical Review D)

   We investigate the transverse energy-energy correlator (TEEC) event-shape observable for back-to-back $\gamma +h$and $Z+h$production in both $pp$and $pA$collisions. Our study incorporates nuclear modifications into the transverse-momentum dependent (TMD) factorization framework, with resummation up to next-to-leading logarithmic accuracy, for TEEC as a function of the variable $\tau =(1+\cos \varphi )/2$, where $\varphi$is the azimuthal angle between the vector boson and the final hadron. We analyze the nuclear modification factor $R_{pA}$in $p\mathrm{Au}$collisions at Relativistic Heavy Ion Collider and $p\mathrm{Pb}$collisions at the Large Hadron Collider. Our results demonstrate that the TEEC observable is a sensitive probe for nuclear modifications in TMD physics. Specifically, the changes in the $\tau$-distribution shape provide insights into transverse momentum broadening effects in large nuclei, while measurements at different rapidities allow us to explore nuclear modifications in the collinear component of the TMD parton distribution functions in nuclei. 

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