Center for Frontiers in Nuclear Science Azimuthal decorrelation in lepton-jet and charged particle multiplicity measurements at HERA Kong Tu, on behalf of H1 & ZEUS Brookhaven National Lab 07.28.2020 1 ICHEP 2020 Proton structure One of the most fundamental building blocks, e.g., proton – is much more complicated than what was originally thought. One of many big questions, • What is the pathway towards uncovering the mystery of confinement? • What is the dynamic picture for partons at high energy? • … ICHEP 2020 2 Angular correlation in pp collisions Dijets angular correlations can probe • Parton radiation effect • Higher order perturbative effects • … Δ� = |� − � | back-to-back jets expects ~ � ! " 3 ICHEP 2020 Angular correlation in pp collisions Dijets angular correlations can probe • Parton radiation effect • Higher order perturbative effects • … Soft gluon Δ� = |� − � | back-to-back jets expects ~ � ! " 4 ICHEP 2020 Angular correlation in pp collisions Dijets angular correlations can probe • Parton radiation effect • Higher order perturbative effects • … Soft gluon NLO calculation describes data very well Δ� = |� − � | back-to-back jets expects ~ � (Phys. Rev. D 92, 094007 (2015)) ! " 5 ICHEP 2020 Application in ep DIS - TMDs (Lepton-proton CM frame) • New idea about looking at azimuthal correlation between scattered lepton and jet – sensitive to transverse momentum dependent parton distributions (TMDs) (Phys. Rev. Lett. 122, 192003 (2019)) ICHEP 2020 6 Application in ep DIS - TMDs (Lepton-proton CM frame) • New idea about looking at azimuthal correlation between scattered lepton and jet – sensitive to transverse momentum dependent parton distributions (TMDs) (Phys. Rev. Lett. 122, 192003 (2019)) Experimental attempt Lepton-jet correlation in ep DIS: • Access small Bjorken-x at HERA • Q2 dependence on TMD evolution • Non-perturbative effects ICHEP 2020 7 More details see Amilkar ZEUS preliminary results Quintero’s DNP talk. Click here Data from HERA-II with 27.6 x 920 GeV2 ep: • Luminosity ~ 330 pb-1 • 10 < Q2 < 350 GeV2 • Elepton > 10 GeV • ET,jet > 2.5 GeV, |etajet| < 1.0 • Ariadne MC model describes data reasonably well • some deviations are seen at lower angle, might be due to gluon radiations ICHEP 2020 8 Taking one step further in ep DIS • How does MC describe HFS particle productions besides Jets? • What’s the role of gluons in particle production? ICHEP 2020 9 Taking one step further in ep DIS • How does MC describe HFS particle productions besides Jets? • What’s the role of gluons in particle production? New idea about probing proton structure at low-x via quantum entanglement in DIS S = ln[xG(x,Q2)] ~ S = - ∑ � � ln �(�) gluon hadron https://www.sciencenews.org/article/experiment-hints- quantum-entanglement-inside-protons (Phys. Rev. Lett. 124, 062001 (2020)) 10 H1 analysis • DIS e+p at 27.6 x 920 GeV2 collisions • 5 < Q2 < 100 GeV2 • 0.0375 < y < 0.6 • Measure charged particle multiplicity distributions, p(N), in bins of y and Q2 • Moments of multiplicity • Hadron entropy (new observable) (Phys. Rev. Lett. 124, 062001 (2020)) • Compare with MC models and entanglement model ICHEP 2020 11 Charged particle multiplicity H1 Preliminary ep s=319 GeV 0 < h* < 4 0.0375<y<0.075 0.0375<y<0.075 0.0375<y<0.075 0.0375<y<0.075 1 1 1 1 • Tracks are within |eta | < 5<Q2<10 GeV2 10<Q2<20 GeV2 20<Q2<40 GeV2 40<Q2<100 GeV2 lab 10-1 10-1 10-1 10-1 1.6 and pt > 0.15 GeV 10-2 10-2 10-2 10-2 P(N) P(N) P(N) P(N) 10-3 10-3 10-3 10-3 10-4 10-4 10-4 10-4 10-5 10-5 10-5 10-5 • Tracks are boosted in 0 10 0.075<y<0.1520 30 0 10 0.075<y<0.1520 30 0 10 0.075<y<0.1520 30 0 10 0.075<y<0.1520 30 1 N 2 2 1 N 2 21 N 2 21 N 2 2 5<Q <10 GeV 10<Q <20 GeV 20<Q <40 GeV 40<Q <100 GeV Hadronic center-of-mass 10-1 10-1 10-1 10-1 * 10-2 10-2 10-2 10-2 P(N) P(N) P(N) P(N) frame (HCM) with |eta | < 10-3 10-3 10-3 10-3 4.0 10-4 10-4 10-4 10-4 10-5 10-5 10-5 10-5 0 10 0.15<y<0.320 30 0 10 0.15<y<0.320 30 0 10 0.15<y<0.320 30 0 10 0.15<y<0.320 30 1 N 1 N 1 N 1 N 5<Q2<10 GeV2 10<Q2<20 GeV2 20<Q2<40 GeV2 40<Q2<100 GeV2 • Compare with DJANGOH 10-1 10-1 10-1 10-1 10-2 10-2 10-2 10-2 P(N) P(N) P(N) P(N) 1.4. RAPGAP 3.1, and 10-3 10-3 10-3 10-3 10-4 10-4 10-4 10-4 PYTHIA 8 10-5 10-5 10-5 10-5 0 10 0.3<y<0.620 30 0 10 0.3<y<0.620 30 0 10 0.3<y<0.620 30 0 10 0.3<y<0.620 30 1 N 1 N 1 N 1 N 5<Q2<10 GeV2 10<Q2<20 GeV2 20<Q2<40 GeV2 40<Q2<100 GeV2 -1 -1 -1 -1 2 10 10 10 10 • Low-Q are not well 10-2 10-2 10-2 10-2 P(N) -3 P(N) -3 P(N) -3 P(N) -3 10 10 10 10 DJANGOH described by MCs RAPGAP -4 -4 -4 -4 10 10 10 10 PYTHIA 8 10-5 10-5 10-5 10-5 H1 data 0 10 20 30 0 10 20 30 0 10 20 30 0 10 20 30 N N N N 12 Hadron entropy Shadron = - ∑ � � �� �(�) DATA and MC comparison H1 Preliminary 0 < h* < 4.0 • High Q2 and high x are in ep s = 319 GeV good agreement with MC • Low-x and lower Q2 are 4 not. Clearly difference is seen. EE S 2 Q2(data,S ) Q2(RAPGAP,S ) Q2(HERAPDF, S ) hadron hadron gluon 2 (5,10) (5,10) 2 GeV 5 GeV2 (10,20) (10,20) 10 GeV2 (20,40) (20,40) 20 GeV2 (40,100) (40,100) 40 GeV2 0 10-4 10-3 10-2 ICHEP 2020 á x ñ 13 Hadron entropy Shadron = - ∑ � � �� �(�) H1 Preliminary 0 < h* < 4.0 • High Q2 and high x are in ep s = 319 GeV good agreement with MC • Low-x and lower Q2 are 4 not. Clearly difference is seen. DATA and theory comparison EE S • Entanglement entropy 2 from gluon density Q2(data,S ) Q2(RAPGAP,S ) Q2(HERAPDF, S ) overpredicted the hadron hadron gluon 2 (5,10) (5,10) 2 GeV 2 magnitude of entropy 5 GeV (10,20) (10,20) 2 10 GeV (20,40) (20,40) 2 20 GeV 2 • Indication of theory of (40,100) (40,100) 40 GeV 0 entanglement entropy still 10-4 10-3 10-2 has room to be improved. ICHEP 2020 á x ñ 14 Summary • First studies of lepton-jet correlation in ep DIS by ZEUS collaboration – sensitive probe to the TMDs • First time measurement of hadron entropy from HFS of charged particles by H1 collaboration – searching for quantum entanglement of partons in ep DIS. (paper will come out by the end of summer) • Both measurements have set a baseline for future experiment of Electron-ion Collider at BNL in ep and eA. • Stay tuned for further developments from H1 and ZEUS as many new projects are on-going! ICHEP 2020 15.