Jets at Hadron Colliders Jet Physics at Hadron

Jets at Hadron Colliders Jet Physics at Hadron Colliders Andrey Korytov Advanced Studies Institute on Symmetries and Spin Prague, July 27 – August 3, 2005 Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders ● ● Hadron Colliders ISR (Intersecting Storage Rings) at CERN Spp. S (Super Proton-Antiproton Synchrotron) at CERN Tevatron at Fermilab LHC (Large Hadron Collider) at CERN Collider Years Particles Co. M Energy Max Luminosity ISR 1971 -1984 pp 60 Ge. V 2 1032 cm-2 s-1 Spp. S 1981 -1990 pp 600 Ge. V 6 1030 cm-2 s-1 Tevatron 1987 -2009 pp 2 Te. V 1032 cm-2 s-1 LHC 2007 - pp 14 Te. V 1034 cm-2 s-1 ● RHIC (Relativistic Heavy Ion Collider) at Brookhaven RHIC 2000 -. . . Andrey Korytov, University of Florida A+A 2 100 N Ge. V Symmetries and Spin, Prague, July 27 – Aug 3, 2005 1027 cm-2 s-1

Jets at Hadron Colliders Tevatron accelerator complex CDF 2 km D 0 Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Tevatron accelerator complex Run I 2001 2002 2003 2004 2005 ● ● 1992 -1996 Co. M Energy 1. 8 Te. V Max L = 2 1031 cm-2 s-1 Int. L = 0. 1 fb-1 Run II ● 2001 -2009 ● Co. M Energy 1. 96 Te. V ● Int. L = 4 -8 fb-1 (by 2009) ● So far: ▬ Max L: ~1032 cm-2 s-1 ▬ Integral L: ~1 fb-1 Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Hadron Collider Detector: CDF (example) • • • Andrey Korytov, University of Florida 3 d vertex coverage: |h|<2 Tracking coverage: |h|<2 Calorimeter coverage: |h|<3. 6 Mini-plug calorimeter: 3. 6<|h|<5. 1 Muon coverage: |h|<1. 5 Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders ● ● ● Main Tools for studying high PT Physics Muons Electrons Photons Jets Missing ET TRACKER: axial view CALORIMETERS: unfolded (h, f)-plane Raw Jet Et = 518 Ge. V Raw Jet Et = 533 Ge. V Jets are messy objects! Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet: from birth to death JET Hadronic showers EM showers Andrey Korytov, University of Florida EACH STAGE IS FULL OF UNCERTAINTIES Pick two partons and their momenta ● parton density functions, PDF Hard Scattering: 2 X ● ● exact matrix element at LO, some at NLO, . . . QCD scale dependence. . . Soft final state radiation ● approximate resummation in all orders of p. QCD: LLA (leading log approximation), NLLA Hadronization ● phenomenological models Calorimeter response ● ● electromagnetic shower for photons hadronic shower for “stable” hadrons Jet identification (and corrections) ● jet finding algorithms Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Finding Algorithms Cone Algorithm: How many jets ●are out there? cluster together calorimeter towers by their “angular” proximity in (h, f) space ● merging/splitting of overlapping cones is not infrared stable (at NNLO) ● ad hoc Rsep=1. 3 to match theory and exp. ● Tevatron Run I legacy Mid. Point Cone Algorithm: ● cone algorithm with modifications improving infrared stability k. T Algorithm: ● cluster together calorimeter towers by their k. T proximity ● infrared stable (no splitting/merging) ● no clusters left out more sensitive to underlying event contribution ● favored choice at e+e- colliders Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Finding Algorithms How many jets are out there? Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders So, how many jets are out there? 3 3 4 5 Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet: How well can we measure it, after all? Net Result: ● corrections: ▬ out-of-cone losses ▬ UE contribution subtraction ▬ is it a clean cut? ● Jet Energy Resolution (stochastic): ● calibration: ▬ test beam ▬ jet-jet energy balance ▬ jet-photon energy balance ▬ are they all directly applicable? Andrey Korytov, University of Florida ● Absolute Scale Uncertainty (systematic): Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Physics at Hadron Colliders SM Physics with jets ● jet production (X+jets) QCD at large energy scales SM Physics of jets ● jet structure QCD at small energy scales SM Physics using jets as a probe ● jet propagation through Quark-Gluon Plasma QCD of dense states QCD and Jets are the key to New Physics ● new physics is likely to be born in a QCD process ● new physics often results in jets in final states ● most of the time, QCD is the major background Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Physics at Hadron Colliders ● Physics with jets (jet production) ▬ Jets (inclusive, dijets, Njets) ▬ Heavy flavor jets ▬ V+jets (W, Z, g) ▬ Diffractive jets ▬ Multi Parton Interaction jets ● Physics of jets (jet stracture) ▬ q/g jet differences ▬ particle momentum distributions ● Jets as a probe of QGP ▬ jet quenching at RHIC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Inclusive jet production Only two variables in the game. . . We choose to study ● ET differential x-section: d /d. ET ● for different h-bins… Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Inclusive jet production: Run I story… Run I data and NLO+CTEQ 3 M ● ● Excess at high ET? Quark compositness? Run I data and NLO+CTEQ 6 M ● CTEQ 6: ▬ New Data: H 1, ZEUS, D 0 (vs. h!), CDF ▬ New methods: Systematic errors included ▬ New features: Errors are available ● no excess, anymore? Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Inclusive jet production: Run II data vs NLO Run II data and theory: ● reasonable agreement with NLO+CTEQ 6. 1 ● déjà vu: “high-ET excess” again? ● ~20% dip at lower ET? (not present in Run I) ● must beat systematic errors down: ▬ Theory: PDFs ▬ Experiment: energy scale Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005 New reach in Run II

Jets at Hadron Colliders • • Inclusive jet production: Run II vs Run I In Ratio, PDF uncertainties largely cancel out. . . The Run II – Run I discrepancy remains, but within energy scale errors. . . Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Tevatron: 1. 8 Te. V vs 630 Ge. V Déjà vu again? ● the current discrepancy “d /d. ET(1. 96) vs. d /d. ET(1. 8)” is disturbingly similar to ● the past discrepancy “d /dx. T(1. 8) vs. d /dx. T(0. 63)” Ratio = d /dx. T(630) / d /dx. T(1800) NLO with varying PDFs CDF (●) and D 0 (○) data Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Cone vs. Mid. Point Cone vs. KT algorithms RUN II PRELIMINARY RESULTS Cone (Run I Cone) CDF, L=177 pb-1 Mid. Point Cone (Run II Cone) D 0, L=378 pb-1 KT CDF, L=385 pb-1 Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jets at LHC Jets up to ET=4 Te. V Huge (x, Q 2) range Tevatron I Tevatron Jets LHC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Dijet production With 5 independent variables in the game (E 1, h 1, E 2, h 2, Df 12), one might want to look at: ● ● dijet mass MJJ dijet axis polar angle cm in dijet Co. M frame azimuthal angle Df 12 … Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Dijets Highest Dijet Mass event (so far) MJJ=1364 Ge. V ET=666 Ge. V ET=633 Ge. V Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Dijets: polar angle (I) Dijet polar angle distribution can disentangle whether the high ET access is due to ● quark substructure: new physics! ● or enhanced PDF f(x) at large x: g(x) at large x is poorly constrained Enhanced PDF f(x) at large x ● increased d /d. ET at high ET (and d /d. MJJ at high MJJ) ● unchanged forward angular distribution characteristic of t-channel exchange a la Rutherford scattering: d. N/d ~1/sin 4 ( /2) Quark substructure results in ● increased d /d. ET at high ET (and d /d. MJJ at high MJJ) ● more central angular distribution Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005 *

Jets at Hadron Colliders Dijets: polar angle (II) Run I Compositness limit: L > 2 Te. V cf. ultimate LHC reach >30 Te. V Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005 *

Jets at Hadron Colliders Dijets: azimuthal angle Df 12 LO in Df NLO in Df - LO is very poor at Df~p/2 and Df~p - NLO fixes Df~p/2, but overshoots at Df~p Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Dijet spin-off: any narrow resonances in MJJ? Plausible new physics scenarios leading to narrow dijet resonances: àAny bumps over a smooth line fit? Nope: many models are excluded with mass in the range 200 -1000 Ge. V Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders 3 -, 4 -, 5 -, 6 -jet production Run I: ● all independent kinematical distributions with up to 6 jets in the final states were checked for consistency with QCD ● no discrepancies outside of the experimental and theoretical systematic uncertainties were found Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Physics at Hadron Colliders ● Physics with jets (jet production) ▬ Jets (inclusive, dijets, Njets) ▬ Heavy flavor jets ▬ V+jets (W, Z, g) ▬ Diffractive jets ▬ Multi Parton Interaction jets ● Physics of jets ▬ q/g jet differences ▬ particle momentum distributions ● Jets as a probe of QGP ▬ jet quenching at RHIC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders b-jet production ● Cross section is known up to NLLO + LLA resummation ● Understanding of the phenomenological B-meson fragmentation function is critical for evaluating B-tagging efficiency Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders b-jet tagging Method ● Jets with tracks forming displaced vertex b-tagging efficiency: ~40% ● decay length distribution e-L/l peaks at 0 b-tagging purity: ~30% ● c-jets ● q/g jets with mis-id or mis-measurements ● invariant mass formed by displaced tracks can be used to evaluate purity Other Methods used: ● hadronic (combined with displaced vertex) ▬ inclusive, Hb→ J/y + X ▬ exclusive, e. g. B+→ J/y + K+ ● semi-leptonic: ▬ Hb → m + X Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders b-jet production: ● ~3% of all jets (almost PT independent) ● agrees with p. QCD: ▬ Pythia Monte Carlo = LO: data/LO ~ 1. 4 (as expected) ▬ NLO comparison is forthcoming Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders b-production: Run I controversy (1) Experiment vs Theory in Run I ● data/theory ~ 3 (excess? exciting!) Theory since Run I: 2000 ● Fixed Order NLO + LL resummation became available ● b-quark fragmentation function updated (LEP data input) ● more resent PDFs 2002 Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders b-production: Run I controversy (2) Experiment vs Theory in Run I ● data/theory ~ 3 (excess? exciting!) Theory since Run I: ● Fixed Order NLO + LL resummation became available ● b-quark fragmentation function updated (LEP data input) ● more resent PDFs Experiment since Run I ● Run I results: not changed ● Run II agrees with Run I Experiment vs Theory now ● coexist in peace. . . Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders b-jet production spin-off: Search for Higgs SM Higgs W q ● likes to couple to heavy particles: ZH, WH are best bets, if any at all, for discovering SM Higgs at Tevatron (t is the best, but hard to produce) ● H->bb is the dominant decay channel W q H b b b Andrey Korytov, University of Florida MSSM Higgs (in most of parameter space) ● Z and W couplings suppressed ● coupling to down-fermions enhanced: bb. H production cross section is large ● H->bb still the dominant decay channel ● Look for multi b-jets! b Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders b-jet production spin-off: Search for Higgs Calibrate your analysis on 2 b-jet events ● heavy flavor bkgd: QCD bbj+X ● mistag: QCD jjj+X ● other bkgd: Zj, tt, bbbb, etc. Search for Higgs in bbb+X ● note: 4 th b-jet is allowed to be missed ● no excess seen: No Nobel Prize (yet) Signal that can be excluded at 95%CL Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Physics at Hadron Colliders ● Physics with jets (jet production) ▬ Jets (inclusive, dijets, Njets) ▬ Heavy flavor jets ▬ V+jets (W, Z, g) ▬ Diffractive jets ▬ Multi Parton Interaction jets ● Physics of jets ▬ q/g jet differences ▬ particle momentum distributions ● Jets as a probe of QGP ▬ jet quenching at RHIC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders EWK vector bosons (W, Z, g) + jets Examples of LO diagrams W or Z or g + jet W or Z ● Smaller subset of diagrams, different mix of initial partons: PDF contribute differently as compared to the plain jet production Theory (on example of W): ● W inclusive: ● W + 1 jet: ● W + 2, 3, 4 jets: can be generated at NNLO level Notes: ● Inclusive distributions are not affected by jet finding uncertainties ● W/Z/g identification algorithms have their own caveats… Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders W + jets Inclusive s(W) Br(W→en) CDF: LO: NNLO: Run I (1. 8 Te. V) 2. 38 0. 24 nb 1. 76 2. 41 2. 50 Run II (1. 96 Te. V) 2. 64 0. 18 nb 1. 94 2. 64 2. 73 LO is significantly off NLO works quite well NNLO makes little difference s(W + N jets) Br(W en): LO QCD works fairly well 1 st jet 4 th Andrey Korytov, University of Florida 3 rd 2 nd Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Z + jets Ratio (Z + N jets) / (Z) agrees well with ● LO Matrix Element (Mad. Graph) + Parton Shower (Pythia) ● MCFM (NLO total x-section) Jet PT in Z+jets events agrees well with ● LO Matrix Element (ALPGEN) + Parton Shower (Pythia) 1 st jet highest p. T in events with N 1 jets 3 rd jet in events with N 3 jets Andrey Korytov, University of Florida 2 nd jet in events with N 2 jets Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Z+jet spin-off: Extra Dimension searches Large Extra Dimensions (ADD) Arkani-Hamed, Dimopoulos, Dvali, Phys Lett B 429 (98) D 0 Analysis G SELECTION CUTS: g, q Je g, q t Leading Jet PT>150 Ge. V |h|<1 2 nd Jet PT<50 Ge. V No e/m candidates MET>150 Ge. V RESULTS: Main background: o Expected Background (Z+jets, W+jets): NB = 100 6(stat) 8(theory) +50%-30% (jet energy scale) o Data: N = 63 No Nobel Prize (yet) Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Physics at Hadron Colliders ● Physics with jets (jet production) ▬ Jets (inclusive, dijets, Njets) ▬ Heavy flavor jets ▬ V+jets (W, Z, g) ▬ Diffractive jets ▬ Multi Parton Interaction jets ● Physics of jets ▬ q/g jet differences ▬ particle momentum distributions ● Jets as a probe of QGP ▬ jet quenching at RHIC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Diffractive Dijets Typical parton-parton interaction ● two partons scatter and produce two jets ● proton and antiproton remnants carry on along the beam line and produce forwardbackward debris ● color strings between outgoing hard-scattered partons and spectator partons break resulting in flow of particles between jets and beam line Typical diffractive interaction ● one or both protons remain intact ● whatever protons exchange with has quantum numbers of vacuum, but still must have QCD as an underlying theory ▬ diffractive cross section is relatively large ▬ hadrons/jets readily produced in such events ● no color strings between outgoing partons and protons are formed resulting in ▬ characteristic rapidity gaps (intervals of pseudorapidity unpopulated with any particles) Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005 often called Pomeron

Jets at Hadron Colliders Double Pomeron Exchange Dijet fraction “Double Pomeron Exchange” h j Non-Diffractive Parton Scattering “Double Pomeron Exchange” Dijets ~ Non-Diffractive Dijets Andrey Korytov, University of Florida h j 10% (ET 2 > 7 Ge. V) Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Diffraction dijets: new twist (diffractive Higgs? ) Khoze, Martin, Ryskin (2002): We can check the model at Tevatron! Higgs b b Clean Signal at LHC ● ~ 3 pb 30 events in 1 yr at L=1033 ● ~ 40 pb (ET>25 Ge. V), with factor of 2 uncertainty ● Signal/Bkgd ~ 3 ● ~100% gg jets Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Diffractive Exclusive Dijets? Expected shape of signal events Mx Dijet Mass Fraction Rjj= Andrey Korytov, University of Florida Mjj Mx Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Diffractive Exclusive Dijets: so does it check? Excluded at 95% CL Martin, Kaidalov, Khoze, Ryskin, Stirling (hep-ph/0409258): ~ 40 pb (ET>25 Ge. V), with a factor of ~2 uncertainty Almost excluded, more statistics is needed. . . Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Physics at Hadron Colliders ● Physics with jets (jet production) ▬ Jets (inclusive, dijets, Njets) ▬ Heavy flavor jets ▬ V+jets (W, Z, g) ▬ Diffractive jets ▬ Multi Parton Interaction jets ● Physics of jets ▬ q/g jet differences ▬ particle momentum distributions ● Jets as a probe of QGP ▬ jet quenching at RHIC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jets from Multi-Parton Interactions Process a: g ● g-jet: Jet 3 cross section a Process b: ● dijet: cross section b Double-parton scattering in single pp collision: ● (g-jet) + (dijet) ● cross section ab Jet 1 Jet 2 ● eff characterizes Impact parameter r Overlapping area A(r) ▬ transverse proton size and density of partons ▬ clumpiness of partons together (the smaller eff, the clumpier the structure is) ▬ x 1 -x 2 correlations for combined pdf f(x 1, x 2): (should eff be x-dependent, it would be a tale tell sign of two-parton correlations) ● if partons are uniformly distributed in a sphere of radius r, related to the total non-diffractive inelastic cross section ~50 mb, then ▬ eff ~ 11 mb Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jets from Multi-Parton Interactions g Jet 3 Jet 1 Jet 2 Single Scattering Contribution Signal selection: ● 3 jets and photon ● match g-jet and jet-jet by best ET balance Double ( gj + jj ) vs single ( 3 jg ) ● The best discriminating distribution is Djangle between PT(g-jet) and PT(dijet) Double Parton Scattering Contribution ▬ PT 0 due to NLO contributions ▬ PT directions do not correlate for two nearly independent interactions ▬ and strongly correlate for single interaction (tend to be back to back) Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Physics at Hadron Colliders ● Physics with jets (jet production) ▬ Jets (inclusive, dijets, Njets) ▬ Heavy flavor jets ▬ V+jets (W, Z, g) ▬ Diffractive jets ▬ Multi Parton Interaction jets ● Physics of jets ▬ q/g jet differences ▬ particle momentum distributions ● Jets as a probe of QGP ▬ jet quenching at RHIC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Fragmentation: Gluon vs Quark jets Difference of Particle Multiplicities in Gluon and Quark jets: r = Nhadrons(gluon jet) / Nhadrons(quark jet) ● calculations (for partons): ▬ various extensions of NLLA: r=1. 5 -1. 7 (depends on Q=Ejet cone) ● data: 15+ papers from e+e ▬ r=1. 0 -1. 5 (not all self-consistent) ● CDF analysis: ▬ dijet events with Mjj~100 Ge. V gluon jet fraction ~60% ▬ g-jet events with Mgj~100 Ge. V gluon fraction ~20% ▬ measure Njj and Ngj inside 15 -30 cone around jet axis ▬ resolve for Ng, Nq and their ratio, RESULT: r ~ 1. 6 0. 2 Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Fragmentation: momenta, multiplicities Momentum distribution of charged particles in jets cone opening angle =0. 47 ● dijet events with well-balanced ET ● 15 -30 cone around dijet axis Two parameter fit (MLLA+LPHD): ● works surprisingly well in wide range of dijet masses ● MLLA Qeff = 230 40 Me. V ☞ k. T-cutoff can be set as low as LQCD ● KLPHD( ) = 0. 56 0. 10 ☞ Nhadrons Npartons Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005 CDF

Jets at Hadron Colliders Jet Physics at Hadron Colliders ● Physics with jets (jet production) ▬ Jets (inclusive, dijets, Njets) ▬ Heavy flavor jets ▬ V+jets (W, Z, g) ▬ Diffractive jets ▬ Multi Parton Interaction jets ● Physics of jets ▬ q/g jet differences ▬ particle momentum distributions ● Jets as a probe of QGP ▬ jet quenching at RHIC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Physics: RHIC Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders RHIC: Jets as a probe of QGP (I) Jet Quenching—sign of Quark-Gluon Plasma? TRIGGER “JET” DIRECTION BACK DIRECTION Hard Collision Jet STAR Tracks with p. T>2 Ge. V Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005 no recoil jet

Jets at Hadron Colliders Conclusions Jet Physics: ● jet production (high p. T QCD) ● jet structure (low p. T QCD) ● jets as a probe of GQP Jet Physics is reach with very diverse phenomena—lots of fun. . . Jet Physics is a challenge, both for theorists and experimentalists. . . Understanding jet physics is the key for discovering new phenomena beyond the Standard Model at hadron colliders (though, no signs yet) Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Backup Slides Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet: Parton Density Functions PDF fa(x, Q) – parton probability density function to find parton a with momentum p=x. P, where ● a—quark (or antiquark) of particular flavor or gluon ● P—proton/antiproton momentum ● Q—transferred momentum PDFs ● not calculable from first principles ● p. QCD does predict Q-dependence ● obtained from global fits (ee, ep, pp, etc) ▬ uncertainties; very large for g(x) at large x ▬ beware of the vicious circle: PDFs are obtained from data and then re-used in data analyses to judge on agreement of theory and experiment Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet: Exact Matrix Element (e. g. , inclusive jets) ● LO (2 2, ~a 2) is available: jet = parton Sample of LO diagrams: ● NLO (2 2 and 2 3, ~a 3) is available: jet = 1 or 2 partons 2 +. . . Interference + +. . . ● NNLO: “soon to become available” for many years… ● Is NLO good enough? ▬ NLO is very far from the actual multiplicity of particles in jets ▬ Merging criteria on whether 2 partons in NLO form one or two jets may be quite different from the experimental definitions: more phenomenological parameters ▬ NLO x-section remains sensitive to the choices of renormalization scale Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jets: more soft radiation? k. T distribution of particles in jets k, gluon momentum k. T=k sin gluon transverse momentum Differential probabilities of gluon emission: 1 Ge. V From data we know that most particles have k. T<1 Ge. V Andrey Korytov, University of Florida any hope? Perturbative methods at k. T<1 Ge. V are doubtful: - as becomes large - also, notice diverging terms Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet: Leading Log Resummations If we push k. T cutoff scale Qcutoff low: ● as gets larger ● colinear/soft divergences lead to large log terms: probability to emit n partons: ● multi-gluon production becomes inevitable at Q~10 Ge. V! (E jet~100) ● resummation techniques in all orders are a-must ● fortunately, theorists managed to account for and resum all orders with the leading-log (C 0) and next-to-leading-log (C 1) precision: ▬ LLA Leading-Log Approximation ▬ NLLA Next-to-Leading-Log Approximation ~ NOTE: some beyond-NLL terms are often included in calculations, which may result in various flavors of NLLA, depending on what was included Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet: Hadronization Transition from parton shower to hadrons—theory does not exist ● hopefully, hadrons inherit partons’ properties. . . Local Parton Hadron Duality Hypothesis ● To make parton-hadron connection closer, can we push Qcutoff to LQCD? Yes, e. g. Modified LLA, or MLLA (actually, NLLA + some extra terms) ● Naively, MLLA+LPHD would imply: ▬ Nhadrons = K * Npartons with K~1 ▬ momentum distribution of hadrons = that of partons ▬ parton-parton correlations (momentum, multiplicity): do they survive hadronization? Transition from parton shower to hadrons—Monte Carlo Generators ● stop parton shower development at Qcutoff ~ 1 Ge. V ● and then do hadronization ▬ completely phenomenological ▬ different MC Generators do it differently! ▬ with many tuning parameters to match data. . . Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet: Detector Response Fluctuations, fluctuations. . . Hadron Calorimeter ● jet: mostly p , p 0 (p 0→gg), ~10% K, few p/n number of particles and their relative composition fluctuate wildly ● em shower is dense, short, with intrinsic fluctuations EM Calorimeter ● had shower is broad and long, with intrinsic fluctuations large ● sampling technology (passive/active media) adds non-negligible fluctuations ● EM Cal response on hadrons is larger than that of Had Cal (different sampling density): varying starting point of had shower gives large fluctuations in the response Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet: How well can we measure it, after all? Before getting to the answer: ● corrections: ▬ out-of-cone losses ▬ UE contribution subtraction ▬ is it a clean cut? ● calibration: ▬ test beam ▬ jet-jet energy balance ▬ jet-photon energy balance ▬ are they all directly applicable? Andrey Korytov, University of Florida Net Result: ● Jet Energy Resolution (stochastic): ● Absolute Scale Uncertainty (systematic): Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Fragmentation: Gluon vs. Quark Jets in Historical Perspective Ratio r = Nch(gluon jet) / Nch(quark jet) r-measurement history 2. 5 CA /CF =9/4 (LLA, NLLA) NLL extensions r = Ng / Nq 2. 0 HRS OPAL SLD ALEPH DELPHI CLEO CDF 1. 5 1. 0 0. 5 0. 0 1985 1990 1995 2000 Year Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Pollution: fake photons Photon id: ● EM Cluster: ▬ ET > 7 Ge. V ▬ HAD/EM < 0. 055+0. 00045 ET ▬ 0 or 1 track with p. T<1+0. 005 ET ● Energy in Isolation Cone DR=0. 4 (excluding EM Cluster) ▬ Cal Energy < 2+0. 005 ET ▬ Track Energy < 5+0. 005 ET Probability for jet to fake photon ~10 -4 to ~10 -3 ● Shower shape ▬ c 2<20 (transverse profile at the depth of shower maximum) Jet faking photon: ● via fragmentation fluctuation ▬ one prompt p 0 ▬ very few and soft p , p 0 in DR=0. 4 Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Jet Pollution: leptons Probability to fake muon ~ 10 -3 -10 -2 per high p. T track Probability to fake tau ~ 10 -3 per jet Probability to fake electron ~ 10 -4 per jet Electron: Muon: Tau (hadronic): ● source of mis-id ▬ fragmentation: p -p 0 overlap with low isolation energy p/K decays b-jets (B→m+X) punchthrough all with low isolation energy Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005 1 -3 prompt p’s with low isolation energy

Jets at Hadron Colliders Hadron Collider Detector: Coordinates y y proton j z x (anti)proton j – azimuthal angle h – pseudorapidity ● h=0 ( =90 ) h=1 ( =40 ) h=2 ( =15 ) ● soft particles are approxumately uniformly distributed along h ● hard-scattered partons may have a boost along the beam line, but Dh= h 1 -h 2 remains Lorentz-invariant with respect to such boosts and is related to the polar scattering angle in the center of mass of scattered partons ● in central region h<1: Dh ~ D LAB Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders Hadron Collider Detector: Concept Detector: ● ● ● Missing ET solenoid inner tracker em calorimeter had calorimeter muon system Muon System Had Calorimeter EM Calorimeter Solenoid Tracker electron Primary Physics Objects: ● ● ● electron photon hadron jet individual charged hadron muon missing ET Andrey Korytov, University of Florida muon photon jet Symmetries and Spin, Prague, July 27 – Aug 3, 2005

Jets at Hadron Colliders RHIC: Jets as a probe of QGP (II) Absorption dependence on the path in GQP axial view (non-central collisions) small suppression large suppression Andrey Korytov, University of Florida Symmetries and Spin, Prague, July 27 – Aug 3, 2005