Brooks, William K.

2024-03-08, Filmer, E. K., Grant, C. M., Jackson, P., Kong, A. X.Y., Pandya, H. D., Potti, H., Ruggeri, T. A., Ting, E. X.L., White, M. J., Gingrich, D. M., Lindon, J. H., Nishu, N., Pinfold, J. L., Cakir, O., Yildiz, H. Duran, Kuday, S., Turk Cakir, I., Sultansoy, S., Adam Bourdarios, C., Arnaez, O., Berger, N., Castillo, F. L., Costanza, F., Delmastro, M., Di Ciaccio, L., Hryn’ova, T., Jézéquel, S., Koletsou, I., Levêque, J., Lewis, D. J., Little, J. D., Lorenzo Martinez, N., Poddar, G., Sanchez Pineda, A., Sauvan, E., Bernardi, G., Bomben, M., Li, A., Li, T., Marchiori, G., Nakkalil, K., Shen, Q., Zhang, Y., Chekanov, S., Darmora, S., Hopkins, W. H., Hoya, J., Love, J., Luongo, N. A., Metcalfe, J., Mete, A. S., Paramonov, A., Proudfoot, J., Van Gemmeren, P., Wamorkar, T., Wang, R., Zhang, J., Cheu, E., Cui, Z., Ghosh, A., Johns, K. A., Lampl, W., Lindley, R. E., Loch, P., Rutherfoord, J. P., Sardain, J., Varnes, E. W., Zhou, H., Zhou, Y., Bakshi Gupta, D., Burghgrave, B., Cardenas, J. C.J., De, K., Farbin, A., Hadavand, H. K., Myers, A. J., Ozturk, N., Usai, G., White, A., Angelidakis, S., Fassouliotis, D., Fountas, L., Gkialas, I., Kourkoumelis, C., Alexopoulos, T., Drivas-Koulouris, I., Gazis, E. N., Kitsaki, C., Maltezos, S., Paraskevopoulos, C., Perganti, M., Cristian Andres Allendes Flores, BROOKS, WILLIAM K., CARQUIN, EDSON, Fernandez Luengo, S.I., Fuenzalida Garrido, S., PEZOA, RAQUEL, Robles Gajardo, C.M., TAPIA, SEBASTIAN, Viaux Maira, N.

ATLAS measured the centrality dependence of the dijet yield using 165  nb−1 of 𝑝+Pb data collected at √𝑠NN=8.16  TeV in 2016. The event centrality, which reflects the 𝑝+Pb impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, 𝑅CP, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The 𝑅CP shows a scaling with the Bjorken 𝑥 of the parton originating from the proton, 𝑥𝑝, while no such trend is observed as a function of 𝑥Pb. This analysis provides unique input to understanding the role of small proton spatial configurations in 𝑝+Pb collisions by covering parton momentum fractions from the valence region down to 𝑥𝑝∼10−3 and 𝑥Pb∼4×10−4.

2024-05-17, Filmer, E. K., Grant, C. M., Jackson, P., Kong, A. X.Y., Pandya, H. D., Potti, H., Ruggeri, T. A., Ting, E. X.L., White, M. J., Gingrich, D. M., Lindon, J. H., Nishu, N., Pinfold, J. L., Cakir, O., Yildiz, H. Duran, Kuday, S., Turk Cakir, I., Sultansoy, S., Adam Bourdarios, C., Arnaez, O., Berger, N., Castillo, F. L., Costanza, F., Delmastro, M., Di Ciaccio, L., Hryn’ova, T., Jézéquel, S., Koletsou, I., Levêque, J., Lewis, D. J., Little, J. D., Lorenzo Martinez, N., Poddar, G., Sanchez Pineda, A., Sauvan, E., Bernardi, G., Bomben, M., Li, A., Li, T., Marchiori, G., Nakkalil, K., Shen, Q., Zhang, Y., Chekanov, S., Darmora, S., Hopkins, W. H., Hoya, J., Love, J., Luongo, N. A., Metcalfe, J., Mete, A. S., Paramonov, A., Proudfoot, J., Van Gemmeren, P., Wamorkar, T., Wang, R., Zhang, J., Cheu, E., Cui, Z., Ghosh, A., Johns, K. A., Lampl, W., Lindley, R. E., Loch, P., Rutherfoord, J. P., Sardain, J., Varnes, E. W., Zhou, H., Zhou, Y., Bakshi Gupta, D., Burghgrave, B., Cardenas, J. C.J., De, K., Farbin, A., Hadavand, H. K., Myers, A. J., Ozturk, N., Usai, G., White, A., Angelidakis, S., Fassouliotis, D., Fountas, L., Gkialas, I., Kourkoumelis, C., Alexopoulos, T., Drivas-Koulouris, I., Gazis, E. N., Kitsaki, C., Maltezos, S., Paraskevopoulos, C., Perganti, M., Tzanis, P., Andeen, T., Burton, C. D., Choi, K., Onyisi, P. U.E., Panchal, D. K., Tost, M., Unal, M., Huseynov, N., Cristian Andres Allendes Flores, BROOKS, WILLIAM K., CARQUIN, EDSON, Fernandez Luengo, S.I., Fuenzalida Garrido, S., PEZOA, RAQUEL, Carolina Robles Gajardo, Tapia Araya, S., VIAUX MAIRA, NICOLAS

Angular correlations between heavy quarks provide a unique probe of the quark-gluon plasma created in ultrarelativistic heavy-ion collisions. Results are presented of a measurement of the azimuthal angle correlations between muons originating from semileptonic decays of heavy quarks produced in 5.02 TeV Pb+Pb and 𝑝⁢𝑝 collisions at the LHC. The muons are measured with transverse momenta and pseudorapidities satisfying 𝑝𝜇T>4  GeV and |𝜂𝜇|<2.4, respectively. The distributions of azimuthal angle separation Δ⁢𝜙 for muon pairs having pseudorapidity separation |Δ⁢𝜂|>0.8, are measured in different Pb+Pb centrality intervals and compared to the same distribution measured in 𝑝⁢𝑝 collisions at the same center-of-mass energy. Results are presented separately for muon pairs with opposite-sign charges, same-sign charges, and all pairs. A clear peak is observed in all Δ⁢𝜙 distributions at Δ⁢𝜙∼𝜋, consistent with the parent heavy-quark pairs being produced via hard-scattering processes. The widths of that peak, characterized using Cauchy-Lorentz fits to the Δ⁢𝜙 distributions, are found to not vary significantly as a function of Pb+Pb collision centrality and are similar for 𝑝⁢𝑝 and Pb+Pb collisions. This observation will provide important constraints on theoretical descriptions of heavy-quark interactions with the quark-gluon plasma.

2024-07-01, Aad, G., Abbott, B., Abeling, K., Abicht, N. J., Abidi, S. H., Aboulhorma, A., Abramowicz, H., Abreu, H., Abulaiti, Y., Acharya, B. S., Adam Bourdarios, C., Adamczyk, L., Adamek, L., Addepalli, S. V., Addison, M. J., Adelman, J., Adiguzel, A., Adye, T., Affolder, A. A., Afik, Y., Agaras, M. N., Agarwala, J., Aggarwal, A., Agheorghiesei, C., Ahmad, A., Ahmadov, F., Ahmed, W. S., Ahuja, S., Ai, X., Aielli, G., Aikot, A., Ait Tamlihat, M., Aitbenchikh, B., Aizenberg, I., Akbiyik, M., Åkesson, T. P.A., Akimov, A. V., Akiyama, D., Akolkar, N. N., Al Khoury, K., Alberghi, G. L., Albert, J., Albicocco, P., Albouy, G. L., Alderweireldt, S., Aleksa, M., Aleksandrov, I. N., Alexa, C., Alexopoulos, T., Alfonsi, F., Algren, M., Alhroob, M., Ali, B., Ali, H. M.J., Ali, S., Alibocus, S. W., Aliev, M., Alimonti, G., Alkakhi, W., Allaire, C., Allbrooke, B. M.M., Allen, J. F., Allendes Flores, C. A., Allport, P. P., Aloisio, A., Alonso, F., Alpigiani, C., Alvarez Estevez, M., Alvarez Fernandez, A., Alves Cardoso, M., Alviggi, M. G., Aly, M., Amaral Coutinho, Y., Ambler, A., Amelung, C., Amerl, M., Ames, C. G., Amidei, D., Amor Dos Santos, S. P., Amos, K. R., Ananiev, V., Anastopoulos, C., Andeen, T., Anders, J. K., Andrean, S. Y., Andreazza, A., Angelidakis, S., Angerami, A., Anisenkov, A. V., Annovi, A., Antel, C., Anthony, M. T., Antipov, E., Antonelli, M., Anulli, F., Aoki, M., Aoki, T., Aparisi Pozo, J. A., Aparo, M. A., Aperio Bella, L., BROOKS, WILLIAM K., CARQUIN, EDSON, Fernandez Luengo, S.I., PEZOA, RAQUEL, Carolina Robles Gajardo, TAPIA, SEBASTIAN, VIAUX MAIRA, NICOLAS

The observation of the electroweak production of single-top-quarks is made using 255 pb−1 of proton-proton collision data recorded at s√=5.02 TeV with the ATLAS detector at the Large Hadron Collider. An event selection is used to identify single-top-quark candidates arising from t-channel production with the top quark decaying semi-leptonically. Events passing the selection are then used to measure the inclusive cross-section for the combined production of single-top-quarks and antiquarks, σ(tq+t¯q), and the ratio Rt between these two. They are measured to be σ(tq+t¯q)=27.1+4.4−4.1(stat.)+4.4−3.7(syst.) pb and Rt=2.73+1.43−0.82(stat.)+1.01−0.29(syst.). The individual single-top-quark (tq) and single-top-antiquark (t¯q) production cross-sections are measured to be σ(tq)=19.8+3.9−3.1(stat.)+2.9−2.2(syst.) pb and σ(t¯q)=7.3+3.2−2.1(stat.)+2.8−1.5(syst.) pb. All measurements are in good agreement with the Standard Model predictions.