Abstract
The pseudorapidity distributions of dijets as functions of their average transverse momentum (pTave) are measured in proton-lead (pPb) and proton-proton (pp) collisions. The data samples were collected by the CMS experiment at the CERN LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. A significant modification of the pPb spectra with respect to the pp spectra is observed in all pTave intervals investigated. The ratios of the pPb and pp distributions are compared to next-to-leading order perturbative quantum chromodynamics calculations with unbound nucleon and nuclear parton distribution functions (PDFs). These results give the first evidence that the gluon PDF at large Bjorken x in lead ions is strongly suppressed with respect to the PDF in unbound nucleons.
| Original language | English |
|---|---|
| Article number | 062002 |
| Journal | Physical Review Letters |
| Volume | 121 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 7 Aug 2018 |
Bibliographical note
Publisher Copyright:© 2018 CERN. for the CMS Collaboration. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP.
Funding
We thank Nestor Armesto, Paukkunen Hannu, Pia Zurita, Petja Paakkinen and Carlos Salgado for the useful discussions and the NLO pQCD calculations with various nPDFs. We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC and thank the technical and administrative staffs at CERN and at other CMS institutes for their contributions to the success of the CMS effort. In addition, we gratefully acknowledge the computing centers and personnel of the Worldwide LHC Computing Grid for delivering so effectively the computing infrastructure essential to our analyses. Finally, we acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RPF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT, and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); NKFIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS and RFBR (Russia); MESTD (Serbia); SEIDI, CPAN, PCTI and FEDER (Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU and SFFR (Ukraine); STFC (United Kingdom); DOE and NSF (USA).
| Funders | Funder number |
|---|---|
| Not added | ST/I505580/1, ST/K003542/1, ST/M004775/1, ST/L005603/1, ST/N001273/1, ST/I003622/1, ST/J005479/1, ST/N000242/1 |
| CPAN | |
| ERC IUT | |
| LNS | |
| MESTD | |
| MON | |
| MSES | |
| MSHE | |
| MoER | |
| PCTI | |
| STAR | |
| Swiss Funding Agencies | |
| TUBITAK | |
| UASLP-FAI | |
| National Science Foundation | 1151640 |
| U.S. Department of Energy | |
| Hispanics in Philanthropy | |
| Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS) | |
| Secretaría de Educación Pública | |
| Türkiye Atom Enerjisi Kurumu | |
| Louisiana Academy of Sciences | |
| Missouri University of Science and Technology | |
| CERN | |
| Thailand Center of Excellence in Physics | |
| Cosmetic Surgery Foundation | |
| Institute for the Promotion of Teaching Science and Technology | |
| Science and Technology Facilities Council | ST/F007434/1, ST/J004871/1, GRIDPP |
| Department of Science and Technology, Ministry of Science and Technology, India | |
| Ministry of Education - Singapore | |
| Department of Atomic Energy, Government of India | |
| Taighde Éireann - Research Ireland | |
| Helmholtz-Gemeinschaft | |
| Deutsche Forschungsgemeinschaft | |
| Fundação de Amparo à Pesquisa do Estado de São Paulo | |
| National Natural Science Foundation of China | |
| Research Promotion Foundation | |
| National Science Council | |
| Fundação para a Ciência e a Tecnologia | |
| Russian Foundation for Basic Research | |
| Coordenação de Aperfeiçoamento de Pessoal de Nível Superior | |
| Academy of Finland | |
| Bundesministerium für Bildung und Forschung | |
| Chinese Academy of Sciences | |
| Austrian Science Fund | |
| Fonds De La Recherche Scientifique - FNRS | |
| Russian Academy of Sciences | |
| Fonds Wetenschappelijk Onderzoek | |
| Consejo Nacional de Ciencia y Tecnología | |
| Ministerio de Economía y Competitividad | |
| Bundesministerium für Wissenschaft, Forschung und Wirtschaft | |
| General Secretariat for Research and Technology | |
| Ministry of Business, Innovation and Employment | |
| Conselho Nacional de Desenvolvimento Científico e Tecnológico | |
| Ministry of Science, ICT and Future Planning | |
| National Research Foundation of Korea | |
| Joint Institute for Nuclear Research | |
| Instituto Nazionale di Fisica Nucleare | |
| National Science and Technology Development Agency | Thailand |
| Secretaría de Educación Superior, Ciencia, Tecnología e Innovación | |
| Universiti Malaya | |
| Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro | |
| Ministry of Science and Technology, Taiwan | |
| National Academy of Sciences of Ukraine | |
| Centre National de la Recherche Scientifique | |
| Ministry of Education and Science | |
| Institute for Research in Fundamental Sciences | |
| Benemérita Universidad Autónoma de Puebla | |
| Commissariat à l'Énergie Atomique et aux Énergies Alternatives | |
| Secretaría de Estado de Investigación, Desarrollo e Innovación | |
| European Regional Development Fund | |
| State Atomic Energy Corporation ROSATOM | |
| Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional | |
| Pakistan Atomic Energy Commission | |
| State Fund for Fundamental Research of Ukraine | |
| Institut National de Physique Nucléaire et de Physique des Particules | |
| Nemzeti Kutatási, Fejlesztési és Innovaciós Alap |