Invariant jet mass measurements in pp collisions at s=200  GeV at RHIC

M S Abdallah ,T Truhlar,X Gou,B Kimelman,A Aparin,G Wang,G Eppley,D Grosnick,M Posik,B Pawlik,A Hamed,W Solyst,F Seck,G Ponimatkin,J Adam,L Didenko,M Shao,A Lebedev,N Elsey,S Kabana,B Stringfellow,D Keane,A Quintero,P Filip,J Porter,S Heppelmann,A Ewigleben,N Schmitz,A Kechechyan,R Fatemi,A Taranenko,P Seyboth,Y Li,J Engelage,S Lan,W Guryn,G Odyniec,Y Hu,G Nigmatkulov,P Sorensen,S Esumi,J Cheng,M Sergeeva,R Nishitani,A Pandav,R Witt,O Eyser,N Xu,R Lacey,M Tokarev,L Kochenda,T Galatyuk,H Caines,I Bunzarov,D Isenhower,E Shahaliev,D Mallick,A Mukherjee,K Jiang,S Margetis,D Tlusty,P Bhagat,J Pluta,E Finch,N Chankova-Bunzarova,E Loyd,A Gibson,C Perkins,L Di Carlo,R Ma,M Strikhanov,C Racz,A Attri,Y Huang,S Trentalange,Y Panebratsev,G Van Buren,S Fazio,P Chaloupka,M Robotkova,J Sandweiss,L Ruan,T Niida,K Kauder,D Kalinkin,Y Fisyak,T Ullrich,Y Zhang,S Harabasz,P Federic,S Mioduszewski,Y Söhngen,W Zha,A Ogawa,G Agakishiev,A Dhamija,J Lauret,F Liu,D Cebra,W Christie,P Parfenov,N Raha,Z Chang,V Prozorova,T Todoroki,X Dong,I Vassiliev,R Pak,R Seto,T Tarnowsky,N Herrmann,V Verkest,D Kincses,Md Nasim,D Kapukchyan,K Yip,R Sikora,Z Ye,B Summa,M Chevalier,Y Han,M Stefaniak,S Salur,H Sako,J Vaněk ,W W Jacobs ,C Feng ,Y Xu,L Pinsky,A Gupta,S Vokál ,N Sahoo ,H Liu,I Mooney,J K Adkins ,O Evdokimov,J Butterworth,Y V Khyzhniak ,M U Ashraf ,Y G ,A R Timmins ,R L Ray ,J H Lee ,J M Landgraf ,L Yi,J C Dunlop ,J L Romero ,H Harrison,J H Kwasizur ,J Bielčík ,P Wang,R S Longacre ,B R Pokhrel ,M Daugherity,N K Pruthi ,F J M Geurts ,H M Spinka ,D P Kikoła ,Z Tu,D B Nemes ,B Surrow,S Chattopadhyay,F Videbæk ,R E Tribble ,A Behera,H S Matis ,A H Tang ,C Kim,W Baker,O D Tsai ,J D Nam ,G Xie,A V Brandin ,W B Schmidke ,J H Thomas ,X Luo,J Fedorišin ,T D S Stanislaus ,Ł Fulek ,M Przybycień ,L Wen,B A Trzeciak ,X P Zhang ,L Kramárik ,W He,Y Yu,I Chakaberia,H Qiu,M Csanád,B K Chan ,K Nayak,A A Derevschikov ,П Кравцов ,S A Voloshin ,W Li,M Zyzak,F G Atetalla ,C Zhang,S S Shi ,L Adamczyk,J C Webb ,J Seger,W J Llope ,Z J Zhang ,I G Bordyuzhin ,A A P Suaide ,X He ,P Liu,Z Tang,E C Aschenauer ,N S Lukow ,X Chen,M M Mondal ,C Yang,J L Drachenberg ,X Cai ,R Licenik,D Zhang,C Li,Z Xu,M D Harasty ,J F Wu ,A Chatterjee,H W Ke ,H Pei,L Kumar,Susumu Sato ,T G Dedovich ,M Simko,P C Weidenkaff ,B R Schweid ,Qingyang Xu ,C Markert,Z Ahammed,R Bellwied,C A Tomkiel ,J Chen,G D Westfall ,Y Ji,Z W Sweger ,S Singha,T Ljubičić ,F-H Chang,R Majka,M I Nagy ,H G Ritter ,E G Judd ,J M Nelson ,M Nie,C A Gagliardi ,S Choudhury,H Zbroszczyk,Q Yang,N G Minaev ,R Lednický ,O V Rogachevskiy ,X Liu,P Tribedy,J Zhao,A Jentsch,H Z Huang ,Z Wang,B S Page ,A Vasiliev ,M L Kabir ,Y Liu,S K Tripathy ,Z Chen,Yang He ,K Gopal,R L Pintér ,Yang Yu ,J Rusňák ,Y Feng,D Y Shen ,Xiao Zhang ,S W Wissink ,Santosh Kumar ,A I Hamad ,F Wang,D G Underwood ,P V Shanmuganathan ,N Magdy,B Xi,S He,M Żurek ,M Calderón De La Barca Sánchez,T Huang,S K Radhakrishnan ,A S Nunes ,D M Anderson ,X Huang,I Upsal,X Liang,B Mohanty,Z Zhang,M J Skoby ,A Kiselev,L V Nogach ,J W Harris ,Y Liang,Y Sun,E P Sichtermann ,X Sun,K N Barish ,A G Knospe ,Z Liu,Vitaly Okorokov ,H J Crawford ,Y Shi,X Li,Y Lin,Y H Leung ,Jordon Rowe Adams ,I Alekseev,D Neff,D Chen,J Putschke,P Szymański ,J H Chen ,J S Wang ,T Shao,H Xu,X Zhu,I Aggarwal,S H Oh ,J Bielčíková ,N Smirnov,T Liu,K Kang,T H Lin ,Y Wu,M Šumbera ,Q Shou ,I Kisel,I M Deppner ,X Ju,Eric A Hoffman ,S Kagamaster,C.d Fu ,Raghav Kunnawalkam Elayavalli ,V Bairathi,A I Sheikh ,Y Wang,D Pawłowska ,Д А Морозов ,C Jena,J Ball ,C Zhou,J D Brandenburg ,L Holub,David J Stewart ,A Bhasin,J B Singh ,F M Fawzi ,Z H Zhu ,Nirmal Ghimire ,D N Svirida ,R G Reed ,H Wieman,Lishuang Ma ,T Nonaka,X Chu,N Shah,M M Aggarwal ,S Huang ,M A Lisa ,S Zhang,L K Kosarzewski ,A Francisco,W Xie,G S Averichev ,Ashok Kumar Pandey ,J Jia,B Srivastava,J Mazer ,T J Humanic

doi:10.1103/physrevd.104.052007

Abstract

We present the first inclusive measurements of the invariant and SoftDrop jet mass in proton-proton collisions at $\sqrt{s}=200$ GeV at STAR. The measurements are fully corrected for detector effects, and reported differentially in both the jet transverse momentum and jet radius parameter. We compare the measurements to established leading-order Monte Carlo event generators and find that STAR-tuned PYTHIA-6 reproduces the data, while LHC tunes of PYTHIA-8 and HERWIG-7 do not agree with the data, providing further constraints on parameter tuning. Finally, we observe that SoftDrop grooming, for which the contribution of wide-angle non-perturbative radiation is suppressed, shifts the jet mass distributions into closer agreement with the partonic jet mass as determined by both PYTHIA-8 and a next-to-leading-logarithmic accuracy perturbative QCD calculation. These measurements complement recent LHC measurements in a different kinematic region, as well as establish a baseline for future jet mass measurements in heavy-ion collisions at RHIC.

Highlights

A hard scattered parton will typically be highly virtual, and will quickly radiate a gluon [1]
We show a PYTHIA-8 partonlevel simulation and a perturbative QCD (PQCD) calculation at next-toleading-logarithmic (NLL) accuracy to emphasize the suppression of NP effects by grooming
We construct two detector response matrices, one for pT;jet and M, and one for pT;jet1 and Mg, and unfold the uncorrected data to particle-level via the ROOUNFOLD package [44] with a regularization parameter of 4. This parameter corresponds to the number of iterations of the Bayesian inference procedure: each subsequent iteration uses as a prior the posterior from the previous iteration, so that larger numbers of iterations yield less reliance on the initial prior distribution given in this case by Monte Carlo simulations

Summary

INTRODUCTION

A hard scattered parton will typically be highly virtual, and will quickly radiate a gluon [1]. The jet mass is a useful quantity in heavy-ion collisions (see [17] for a previous measurement at the LHC), in which any hard scatters occur before the hot, dense, colored QCD medium is formed. The partons, which carry color charge, interact with the medium which may temporarily increase the virtuality of the jets causing an increase in gluon radiation (increasing the jet mass), while on the whole, virtuality will decrease more quickly in the medium (decreasing the jet mass) [17] This measurement will serve as a vacuum baseline for a future measurement in heavy-ion collisions, in which medium modification of the jet mass in a hot, dense nuclear environment may be observed [27]. We show a PYTHIA-8 partonlevel simulation and a PQCD calculation at next-toleading-logarithmic (NLL) accuracy to emphasize the suppression of NP effects by grooming

EXPERIMENTAL SETUP

CORRECTION FOR DETECTOR EFFECTS

SYSTEMATIC UNCERTAINTIES

RESULTS

SUMMARY

Methods