Measurement of dijet azimuthal decorrelation in pp collisions at root s=8 TeV
BMWFW (Austria) ; FWF (Austria) ; FNRS (Belgium) ; FWO (Belgium) ; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) ; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ; MES (Bulgaria) ; CERN ; CAS (China) ; MoST (China) ; NSFC (China) ; COLCIENCIAS (Colombia) ; MSES (Croatia) ; CSF (Croatia) ; RPF (Cyprus) ; MoER (Estonia) ; ERC IUT (Estonia) ; ERDF (Estonia) ; Academy of Finland (Finland) ; MEC (Finland) ; HIP (Finland) ; CEA (France) ; CNRS/IN2P3 (France) ; BMBF (Germany) ; DFG (Germany) ; HGF (Germany) ; GSRT (Greece) ; OTKA (Hungary) ; NIH (Hungary) ; DAE (India) ; DST (India) ; IPM (Iran) ; SFI (Ireland) ; INFN (Italy) ; MSIP (Republic of Korea) ; NRF (Republic of Korea) ; LAS (Lithuania) ; MOE (Malaysia) ; UM (Malaysia) ; CINVESTAV (Mexico) ; CONACYT (Mexico) ; SEP (Mexico) ; UASLP-FAI (Mexico) ; MBIE (New Zealand) ; PAEC (Pakistan) ; MSHE (Poland) ; NSC (Poland) ; FCT (Portugal) ; JINR (Dubna) ; MON (Russia) ; RosAtom (Russia) ; RAS (Russia) ; RFBR (Russia) ; MESTD (Serbia) ; SEIDI (Spain) ; CPAN (Spain) ; Swiss Funding Agencies (Switzerland) ; MST (Taipei) ; ThEPCenter (Thailand) ; IPST (Thailand) ; STAR (Thailand) ; NSTDA (Thailand) ; TUBITAK (Turkey) ; TAEK (Turkey) ; NASU (Ukraine) ; SFFR (Ukraine) ; STFC (United Kingdom) ; DOE (USA) ; NSF (USA) ; Marie-Curie programme ; European Research Council ; EPLANET (European Union) ; Leventis Foundation ; A. P. Sloan Foundation ; Alexander von Humboldt Foundation ; Belgian Federal Science Policy Office ; Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium) ; Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium) ; Ministry of Education, Youth and Sports (MEYS) of the Czech Republic ; Council of Science and Industrial Research, India ; HOMING PLUS programme of the Foundation for Polish Science ; European Union, Regional Development Fund ; OPUS programme of the National Science Center (Poland) ; Compagnia di San Paolo (Torino) ; MIUR (Italy) ; Thalis programme - EU-ESF ; Aristeia programme - EU-ESF ; Greek NSRF ; National Priorities Research Program by Qatar National Research Fund ; Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University (Thailand) ; Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand) ; Welch Foundation ; Science and Technology Facilities Council ; MIUR (Italy): 20108T4XTM ; Welch Foundation: C-1845 ; Science and Technology Facilities Council: ST/N001273/1 ; Science and Technology Facilities Council: ST/K001256/1 ; Science and Technology Facilities Council: GRIDPP ; Science and Technology Facilities Council: ST/I003622/1 GRIDPP ; Science and Technology Facilities Council: ST/M004775/1 ; Science and Technology Facilities Council: ST/H000925/1 ; Science and Technology Facilities Council: ST/K001639/1 ; Science and Technology Facilities Council: ST/K003224/1 CMS Upgrades ; Science and Technology Facilities Council: ST/L005603/1 ; Science and Technology Facilities Council: CMS ; Science and Technology Facilities Council: ST/I000305/1 ; Science and Technology Facilities Council: PP/E002803/1 ; Science and Technology Facilities Council: ST/N000242/1 ; Science and Technology Facilities Council: PP/E000479/1 ; Science and Technology Facilities Council: ST/I003622/1 ; Science and Technology Facilities Council: ST/K001639/1 CMS Upgrades ; Science and Technology Facilities Council: ST/J004871/1 ; Science and Technology Facilities Council: ST/M004775/1 GRIDPP ; Science and Technology Facilities Council: ST/K001531/1 ; Science and Technology Facilities Council: ST/H000925/2 ; Science and Technology Facilities Council: ST/K003542/1 GRID PP ; Science and Technology Facilities Council: ST/M002020/1 ; Science and Technology Facilities Council: ST/J005479/1 ; Science and Technology Facilities Council: ST/N000250/1 ; Science and Technology Facilities Council: ST/K003542/1 GRIDPP ; Science and Technology Facilities Council: ST/K003542/1 ; A measurement of the decorrelation of azimuthal angles between the two jets with the largest transverse momenta is presented for seven regions of leading jet transverse momentum up to 2.2. The analysis is based on the proton-proton collision data collected with the CMS experiment at a centre-of-mass energy of 8 corresponding to an integrated luminosity of 19.7. The dijet azimuthal decorrelation is caused by the radiation of additional jets and probes the dynamics of multijet production. The results are compared to fixed-order predictions of perturbative quantum chromodynamics (QCD), and to simulations using Monte Carlo event generators that include parton showers, hadronization, and multiparton interactions. Event generators with only two outgoing high transverse momentum partons fail to describe the measurement, even when supplemented with next-to-leading-order QCD corrections and parton showers. Much better agreement is achieved when at least three outgoing partons are complemented through either next-to-leading-order predictions or parton showers. This observation emphasizes the need to improve predictions for multijet production.