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Understanding Jet quenching and Medium-response via dihadron correlations

Understanding Jet quenching and Medium-response via dihadron correlations. Df. Jiangyong Jia Stony Brook University & BNL. Thanks Fuqiang Wang for inputs. Medium. Jet. ?. Mostly based on PHENIX paper: nucl-ex/0801.4545. Deer’s antler. 四不像 The “four-unlikes” Pere david’s deer.

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Understanding Jet quenching and Medium-response via dihadron correlations

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  1. Understanding Jet quenching and Medium-response via dihadron correlations Df Jiangyong Jia Stony Brook University & BNL Thanks Fuqiang Wang for inputs Medium Jet ? Mostly based on PHENIX paper: nucl-ex/0801.4545

  2. Deer’s antler 四不像 The “four-unlikes” Pere david’s deer Horse’s head Donkey’s tail Cow’s hoof

  3. Jet quenching & medium response 1 Flow+Recombination RAA 0.2 Jet fragmentation Suppressed Jet + hump Jet + ridge 3 5 d+Au pT Au+Au 0-5% 8 < pT(trig) < 15 GeV/c pT(assoc)>6 GeV Dissipation of lost energy in medium Fragmentation of jets with minimal eloss * The mechanisms for single hadron production are important for dihadron and vice versa

  4. pT Scan: evolution of jet quenching and medium response pTb Hard region (jet) Study the pTa x pTbdependence of the four components Soft region (medium) pTa Df (rad) Head region (suppressed jet) Shoulder region (hump) Near region (jet+ridge)

  5. pT Scan: evolution of jet quenching and medium response Increase partner pT Dip develops Yield suppressed Yield enhanced Increase trigger pT Jet reemerges Can all the features fit in the four-components picture?

  6. Away-side pT Scan pTb Hard region (jet) pt,a pt,b>5 1<pt,a pt,a<4 Soft region (medium) pTa RHS = Head_yield/shoulder_yield (area normalized) • 1<pTa,b < 4 -> RHS<1 -> Shoulder region dominant! • pTaor b >5 -> RHS>1 -> Head region dominant! • pTa or b < 1 -> RHS~1 RHS>1 RHS<1 Competition between “Head” (Suppression) and “shoulder” (enhancement) Shoulder is important up to ~4 GeV/c

  7. Near-side pT Scan • For low pT region • Au+Au shape in Dh is broader than for pp • Au+Au yield is enhanced, especially at large Dh. • For high pT region • Dh shape/yield is similar between Au+Au and pp The ridge component is important to ~4 GeV/c Jet fragmentation takes over at higher pT.

  8. Spectra slope at shoulder region arxiv:0705.3238 [nucl-ex] Phys.Rev.C77:011901,2008 Mean-pT at intermediate pT (1<pTb< 5) 4<pTa<5 3<pTa<4 2<pTa<3 Shoulder slope ~0.45 GeV/c, independent of trigger pT

  9. Near-side slope John Chen poster Ridge slope is slightly harder than the shoulder J. Putschke QM06 Jet Ridge 0.44 GeV/c 0.36 GeV/c

  10. Connection between ridge and shoulder • Their particle compositions are similar to bulk. Near-side Away-side 0712.3033 nucl-ex Away_energy Near_energy 0.5<0.7 * • Ridge and shoulder persist up to pTa,pTb~4 GeV/c • They have similar slope (ridge is slightly harder) • Ridge & Shoulder energies are roughly balanced in a given Dh slice. 0.5<0.7 John Chen poster

  11. Energy dependence for shoulder & ridge * Head200 GeV  Head17.2 GeV Shoulder200 GeV 2x Shoulder17.2 GeV Near200 GeV  8 x Near17.2 GeV At SPS Smaller jet quenching+Stronger Cronin -> Less suppression in Head Smaller medium component -> Smaller ridge/ Shoulder |h|<0.35 0.1<h-hCM<0.7 Df RAA at SPS is totally different, dominated by Cronin effect Ridge is almost gone at SPS energy, the shoulder due to kT broadening? Energy scan is important!

  12. Quantify the medium modifications Both scales with Ncoll per-jet yield IAA is a good quantity at high pT (per-trigger yield = per-jet yield) but is diluted by soft triggers at low pT.  per-trig yield * = per-trig yield

  13. Iaa vs pT Low pT trigger Dilution of soft triggers: T-T recombination / triggering on medium response. High pT trigger IAA~1 Near side IAA IAA~ RAA Away side

  14. Dilution of soft triggers IAA not symmetric wrt trigger/partner pT selection Near-side Since one particle is high pT, hadron pair come from jets emitted near surface The second particle in the pair also comes from surface. But the low pT triggers in per-trigger yield include all soft hadrons.

  15. Dilution to ridge scaled scaled * Scale up the Au+Au by 1/IAA(pTa), then subtract pp Near-side ~consistent with pp jet + roughly flat ridge

  16. Another example: Dilution effect in dAu g g 1/Ntrig dN/d(Δf) Forward Backward q q Au STAR Preliminary d Small x Large x * Large x Small x Triggers: h~0, 3 GeV/c partners: h~3, 0.2 GeV/c Fuqiang CGC suppress num. of forward-scattering Per-trigger yield p-p : 1/2 Au-side: 1/3 d-side: 2/3 Df Dilution effect due to trigger counting! Do not need recombination

  17. Geometrical bias? 8 < pT(trig) < 15 GeV/c pT(assoc)>6 GeV Au+Au 0-5% d+Au Df Df ridge Mach cone * Low pT correlated pairs Bulk emission High pT correlated pairs Surface emission

  18. Geometrical bias? 8 < pT(trig) < 15 GeV/c pT(assoc)>6 GeV Au+Au 0-5% d+Au Low pT correlated pairs Bulk emission High pT correlated pairs Surface emission • Low pT triggers may from cone/ridge surface bias reduced! • Each side contain both ridge and cone contributions

  19. Jet contribution @ low pT 1 Flow+Recombination RAA 0.2 Jet fragmentation JAA 3 5 pT Medium response increase the pair yield at low pT 1 pTa,pTb * Quantify the jet contribution in two-particle momentum space Help understand the particle production mechanism

  20. Near side pair yield modification: JAA • Pair yield scale faster than Ncoll at lowpTa+pTb • These pairs are remnants of quenched jets. Reach same level (RAA) at High pTb • Approximately scales with pTsum=pTa+pTb (since coming from same jet)

  21. JAA @ away-side head region • Low pT pair yield is not suppressed! • Away-side JAA ~ RAA2 at large pT. • away-side jet IAA ~ inclusive jets RAA JAA(pTa,pTb)

  22. 3-p correlation telling the same story? 2D Au+Au Central 0-12% Triggered * D~1.1 D~1.36 Exclusive process selects very different kinematical region and phase space

  23. RP dependence at low pT STAR 3<pTtrig<4GeV/c & 1.0<pTasso<1.5GeV/c 20-60% • Rich dependence patterns of medium response on trigger orientation • PHENIX show jet function, need to ~x (1+2v2trigcos2Df) to compare. • V2/V4 systematics are clearly important!! (enter linearly) M. McCumber, A.Feng, Session VIII, Feb. 5

  24. Models for medium response * • Production mechanisms of associated hadrons • New particle creation: feedback of shower gluons, cerenkov gluons • Local heating: bending jet, momentum kick, Mach cone, backsplash, Glasma bending, coupling to transverse or longitudinal flow etc. • Residual correlations with geometry: elliptic flow (subtracted), correlation between radial flow boosted beam and surfaced emitted transverse jet. • Easier to generate large yield by pickup from the bulk (since no particle production is required) • We know the pair yield is enhanced at low pt. • Supported by the property of the ridge/cone (PID, slope etc) • Mechanisms for ridge and shoulder may well be related.

  25. Final remarks: Jet quenching & medium response • Jet @ High pT, surface biased, eloss mechanism is constrained indirectly from those with little eloss • Medium response @ Low pT, no surface bias, directly sensitive to energy loss process. • The energy loss mechanism affects characteristics of medium response, example: collisional/radiative <-> momentum kick/gluon feedback. • Different medium response mechanism may require different energy loss scenario. • Energy loss and energy dissipation to the medium are modeled separately. But there shouldn’t be a strict separation of scale, especially for intermediate pT. • Need a unified framework that include both jet quenching & medium response, and can describe correlation data at all pT. More details: M. McCumber, Session VIII, Feb. 5 H.Pei, A.Adare, SessionIX, Feb.8 Poster 23,24

  26. Backup

  27. Constraining the eloss dynamics Yield p+p A+A pT • Absorption • Longer path for away-side jet, IAA<RAA • Independent of spectra shape • Left shift • Stronger energy loss, IAA>RAA • Flatter away-side spectra IAA<RAA • Data suggests IAA ~ RAA • Flatter spectra compensated by bigger energy loss • By combing IAA and RAA, one gain some sensitivity on energy loss. Case I Case II Shift to left Absorption Downward shift nucl-ex/0703047 dn/dpt ~(1/pt)9 for single spectra dn/dpt ~(1/pt)5 for away-side spectra 50% bigger

  28. High pT: jet fragmentation 8 < pT(trig) < 15 GeV/c pT(assoc)>6 GeV Au+Au 0-5% d+Au Per-trigger yield H. Zhang, J.F. Owens, E. Wang and X.-N. Wang , PRL 98(2007)212301 • Observed jet are those “do not” suffer much energy loss. • Near-side: surface emission • Away-side: tangential/punch-through emission. Iaa~Raa, consistent with energy loss calculation

  29. Low pT: medium response to jet Df (rad) • Away-side: strongly modified shape and yield • Suppressed jet (head region) + medium-induced component (Shoulder region) • Near-side: elongated structure in Dh, enhancement in yield. • Surface Jet + medium-induced component (ridge) STAR

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