Observation of medium-induced yield enhancement and acoplanarity broadening of low-$p_\mathrm{T}$ jets from measurements in pp and central Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV

• Published in: Physical review letters 2024, Vol.133 (2)
• Main Authors: Acharya, Shreyasi, Adamova, Dagmar, Aglieri Rinella, Gianluca, Agnello, Michelangelo, Agrawal, Neelima, Ahammed, Zubayer, Ahmad, Shakeel, Ahn, Sang Un, Ahuja, Ishaan, Akindinov, Alexander, Al-Turany, Mohammad, Aleksandrov, Dmitry, Alessandro, Bruno, Alfanda, Haidar Masud, Alfaro Molina, Jose Ruben, Ali, Bushra, Alici, Andrea, Alizadehvandchali, Negin, Alkin, Anton, Alme, Johan, Alocco, Giacomo, Alt, Torsten, Altamura, Anna Rita, Altsybeev, Igor, Anaam, Mustafa, Andrei, Cristian, Andreou, Nicodemos, Andronic, Anton, Anguelov, Venelin, Antinori, Federico, Antonioli, Pietro, Apadula, Nicole, Aphecetche, Laurent Bernard, Appelshaeuser, Harald, Arata, Carolina, Arcelli, Silvia, Aresti, Mauro, Arnaldi, Roberta, Martins Campos Almeida Arneiro, Jhoao Gabriel, Arsene, Ionut Cristian, Arslandok, Mesut, Augustinus, Andre, Averbeck, Ralf Peter, Azmi, Mohd Danish, Baba, Hitoshi, Badala, Angela, Bae, Joonsuk, Baek, Yongwook, Bai, Xiaozhi, Bailhache, Raphaelle Marie, Bailung, Yoshini, Balbino, Alessandro, Baldisseri, Alberto, Balis, Bartosz, Banerjee, Debjani, Banoo, Zarina, Barbera, Roberto, Barile, Francesco, Barioglio, Luca, Barlou, Maria, Barman, Banajit, Barnafoldi, Gergely Gabor, Barnby, Lee Stuart, Ramillien Barret, Valerie, Barreto de Oliveira Campos, Leonardo, Bartels, Clara, Barth, Klaus, Bartsch, Esther, Bastid, Nicole, Basu, Sumit, Batigne, Guillaume, Battistini, Daniel, Batyunya, Boris, Bauri, Dibakar, Bazo Alba, Jose Luis, Bearden, Ian Gardner, Beattie, Caitlin, Becht, Pascal, Behera, Debadatta, Belikov, Iouri, Bell Hechavarria, Ailec, Bellini, Francesca, Bellwied, Rene, Belokurova, Svetlana, Vasquez Beltran, Yael Antonio, Bencedi, Gyula, Beole, Stefania Maria, Berdnikov, Yaroslav, Berdnikova, Anastasia, Bergmann, Luisa, Besoiu, Mihaela Gabriela, Betev, Latchezar, Bhaduri, Partha Pratim, Bhasin, Anju, Bhat, Mohammad Asif, Bhattacharjee, Buddhadeb, Bianchi, Livio, Bianchi, Nicola, Bielcik, Jaroslav, Bielcikova, Jana
• Format: Article
• Language: English
• Subjects: High Energy Physics - Experiment; Nuclear Experiment; Physics
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.133.022301

The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum (high $p_{\rm T}$) hadron trigger in proton$-$proton and central Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV. A data-driven statistical method is used to mitigate the large uncorrelated background in central Pb$-$Pb collisions. Recoil jet distributions are reported for jet resolution parameter $R=0.2$, 0.4, and 0.5 in the range $7 < p_{\rm T,jet} < 140$ GeV$/c$ and trigger$-$recoil jet azimuthal separation $\pi/2 < \Delta\varphi < \pi$. The measurements exhibit a marked medium-induced jet yield enhancement at low $p_{\rm T}$ and at large azimuthal deviation from $\Delta\varphi\sim\pi$. The enhancement is characterized by its dependence on $\Delta\varphi$, which has a slope that differs from zero by 4.7$\sigma$. Comparisons to model calculations incorporating different formulations of jet quenching are reported. These comparisons indicate that the observed yield enhancement arises from the response of the QGP medium to jet propagation.