# Presentation: 492212

## Probing RHIC Matter with High pT Spectra and Correlations of Jets w/ Other (non-Jet!) Probes

- Justin Frantz
- SUNY Stony Brook
- ISMD 2007
- 08/08/07

- Thanks to the organizers!

## Outline

- “Garbage Collection” talk (not garbage – everything not covered elsewhere?)
- Latest Results from high pT Hadron Spectra
- Lower energy suppression data
- Comments on Eloss diff btw *q/g *(color factor)
- ...in relation to PHENIX search for Jet-Medium 
- Direct photon high pT spectra
- New lower energy direct photon
- Direct photon-jet correlations at RHIC
- A slide on STAR heavy flavor – jet correlation measurement

- Oscar the Grouch

## Argh... these plots again?

- Reminder: Raa = A+A / Nscaling*p+p

- YES! we see high pt suppression!

## OK, use it constrain theory parameters

- QM’06: fitting analysis
- Latest (last couple weeks) re-analysis confirms qhat not well constrained esp. on high side
- Soon to be published, along with finalized  spectra

**Model values from C.Loizides hep-ph/0608133v2**

## Wait?  Is that it?

- No... my feeling is that we say “RAA is *fragile*,  NEXT...”
- RAA vs pT != All Spectra Measurements
- Stil a lot of interesting results in the high pT single particle rates...
- What’s new? Lot’s of stuff...
- New Questions arising: *e.g.* role of shadowing– (direct photon data) ?
- Energy, system size studies being somewhat forgotton now? (by Theory and Experiment)

- Refresh our memory and look at some new developments

## Substantial change
still large sys errors (change ~covered) – errors too big?
How do (other) Eloss calc’s compare vs Energy

- Substantial change
- still large sys errors (change ~covered) – errors too big?
- How do (other) Eloss calc’s compare vs Energy

- New 62.4 GeV RAA Updated

- Old RAA used reference from fit of many disagreeing datasets
- New *measured* Run5 p+p reference

- STAR p+p   ref underway

## Two Energies

- Can we  (simultaneously?) fit both energies within one model?
- Quantify more details of other Eloss ingredients
- If final relative systematics are too big,                          more cleverly cancel Glauber systematics ?
- Combinations of RAA and RCP?

- Reminder: Rcp = A+Acentral / Xscaling*A+Aperipheral

- STAR Prelim *h*

**62.4 ****200**

## Energy Loss Models: Ingredients

- Different models have dependence on various ingredients which should vary as fn of *s*
- e.g. Energy Density...
- ...Dynamic medium motion, Temperature, Initial state effects...

- Nuclear Physics A Volume 757, Issues 1-2 , 8 August 2005, Pages 184-283

- From PHENIX White Paper...

## Much lower (SPS!) Energy...

- Recent PHENIX Result for √sNN 22 GeV Cu+Cu.  STAR data also iminent
- Same fitting for *p+p* ref, but 22 GeV fit more reliable
- Eloss models Cronin fits this data?

## Or even Eloss -- there is some?

- Or even Eloss -- there is some?

- Recent SPS result shows suppression if compared to Cronin enhanced p+A (fake “Raa”)
- But Cronin scaling w/ Ncoll can’t be trusted quantitatively
- Interesting:  if we make same ratio in RHIC 200, we’d see 20 % less suppression (shadowing influence)

- PHENIX 200 GeV 0

- Point:  should be trying to understand these non-Eloss suppression influences more quantitatively!

## System Size or Centrality Dep?

- First look: same suppression behavior vs system size...
- Need to verify whether this holds up under ***final*** errors/analyses
-  *e.g.* PHENIX points hint to be non-scaling?

**p****T****>6 GeV/*****c***

## ~New Q: Color Charge Dep: q vs g?

- B. Mohanty talk Monday:
- Recent AAK Frag fn. set including STAR data: protons from glue frag (hep-ph/0702250_)_
- Should see different suppression for protons/pions
- Not seen in data?  (Within errors)

- STAR

## Color Charge Dep: q vs g?

- Caveats
- Frag fn fits have large uncertainty
- Inclusion of all ingredients (expansion, time) dependence can reduce the effects in real Eloss models? (e.g. Vitev PLB 639 (2006) 38)
- qg/gq Conversion in the medium?
- Liu, Ko (nucl-th/0607047)
- I want to point out a constraint that already exists

*g**p* FF

- _hep-ph/0702250_

## q/gg/q Conversion Calculations

- Factors of 4-6 enhancement of Conversion rates required to explain

- As jets traverse the medium their q/g identity is blurred--conversion

## Constraint: Medium Induced Gamma

- These *q/g* conversion calc’s are very similar to another calculation:
- “Direct” Photon medium enhancement in 4-6 GeV/c pT range
- Basic jet parton (q/g) on medium q/g “targets” cross sections from NLO
- Folded with thermal distribution of medium

- For photons: “Canary” effect from  talk yesterday (Barwick): intrinsically small rate for photon production means sizable addition even if small effect for jets

## “Jet-Medium” Photons

- “Jet-Medium” Photons

- Jet to Conversion
- Model: q jets traversing q/g bath convert (Kinematics: small *u* dominates:  *p**** ≈ p**q*)  First calc Fries, et. al./ more complete treatment w/ Turbide,Gale et. al. (hep-ph/0508201)
- Fragmentation / Bremstrahlung 
- Jet Eloss implies suppression of Frag  but Zakarov (hep-ph/0405101)
- /others predict enhancement

- w/o suppresion

- Direct 

## Jet-medium Enhancement Tested...

- At mid pT enhancement predictions disfavored (*ETD-HIC* ~2 wks ago statement: can be made consistent)
- However, factor of 4 ruled out?
- Q’s about nature of the medium/ radiative Eloss?
- At high pT data favors standard suppression predictions, not enhancement

**Notes:**
This relates back to p+p p+A reference slide

## Direct Photon v2

- Jet suppression should cause same v2 for normal frag as for *h*
- Enhancements should have ***negative*** v2
- Not seen in the data...

- Turbide, et.al

**PHENIX Preliminary**

**PHENIX Preliminary**

- Check w/ more scrutiny for finalization: odd suppression pattern vs cent.?

## Color factorvs Reaction Plane?

- Suggestion: look at proton ratios as a function of reaction plane
- Shed some light on color factor question?
- e.g. if *q/g* conversion phenomena exists/is important, it should be path length dependent in the same way as for Jet Medium ...

- Reminder: Reaction Plane = measurable A+A event plane

## Reaction Plane (RP) Dependence

- v2 @ high pT:   RP Dependence of Eloss
- Physics: Study More Pathlength Dependence Many Measurements of high pT v2/Raa or “Raa vs RP”
- v2 focus has been low pt hydro regime
- Need to study high pt, together with theory (several predictions: Majumder et al, Renk et al.)
- Improved precision needed in data

- Renk et. al. nucl-th/0611027

## Direct Gamma @ high pT

- Considerable interest in high pT behavior
- Shadowing/Isospin effect? (***pre***dicted by Arleo (JHEP 0609 015 (2005))
- Questions of Initial State, shadowing effects in general for A+A
- Recent global re-analysis of nuclear PDF’s
- Impact parameter (cent.) dependent nuclear PDF’s?
- New measurement of 62.4 GeV Au+Au Direct 
- Consistent w/ Binary Scaled NLO

## xT scaling

- xT scaling

- Lower pT, 62.4 GeV data ~same xT as 200 GeV
- p+p ref spectra follow xT scaling
- Comparison hints that shadow/Init. State effect present

- NLO Direct  Spectra

- pT

- xT

## Charm, Heavy Q?

- Heavy quark Eloss will be discussed tomorrow
- Same as light q/g?
- 2-particle correlation method being applied

- Main point so far: c/b separation (fit nearside)
- What about awayside IAA?
- Future: study associated jet in A+A

- Suppression

*p+p*

## -jet @ RHIC

- -jet @ RHIC

- Cleaner determination of fragmentation modification (E == Ejetorig)~ better constrain Eloss models

- IAA

- w/ Eloss

**F. Arleo hep-ph/0601075**

- Trigger  don’t have same surface bias, thus should help constrain Eloss geometry

- IAA of Awayside yield of Direct  triggers

**Renk.. hep-ph/0607166**

## RHIC-Jet Methods

- PHENIX Au+Au 200 GeV

*R***

- incorporate  PHENIX Direct  R measurement

_**PHENIX:**_

- Statistical Subtraction w/ 2-p  Correlations (remove meson decay contribution to inclusive photon corr)

_**STAR:**_

- Use Shower Shape discrimination +  measurement

- Assume NearSide direct yield = 0  direct fraction from NS reduction

## -jet First Results: PHENIX

- -jet First Results: PHENIX

- PHENIX Au+Au compared to p+p
- Cu+Cu now available

- Run 7 Statistics on Tape: ~3x
-  + use 0/decay  as associated:                                                	another  x 2
- IAA should be possible

- + other improvements

## -jet First Results: STAR

- -jet First Results: STAR

- Integrated Away-side yields:
- STAR/PHENIX p+p yields consistent (STAR trigger bin higher)
- PHENIX Au+Au consistent with expected suppression

- p+p

## Finalizing the Result: decay (-h) 

- Finalizing the Result: decay (-h)

- Systematic from contribution
- PYTHIA difference in  frag surprising (more than *m**T*)
- Data measurement performed!
- First -h measurement @ RHIC

- p+p

- Daughter-h

- Parent-h

## Recent Improvements in p+p

- Slope difference ~ promising.  Diff. sensitivity to frag etc.
- “Tagged” quark jets: Difference btw glue and quark jets? (plenty of other reasons of course)
- ... more in search for the color factor (*g* vs *q*) in Eloss

- w/ more stats, eta measured, multiple trigger bins

## Using Tagged Quark Jets (to come)

- More information in this direction:
- Check conclusion that “all baryons are from glue jets”
- STAR method can accomodate this measurement nicely also—more associated pT coverage than PHENIX

- Direct  pt 5-7 GeV/c
- pTa 1-2 GeV/c

- Under construction

- (prompt)

- PHENIX

## Summary of Main Points

- There is still life left in high pT spectra!
- New energy dep. data can contrain Eloss models and/or their “ingredients” : let’s not forget about this!
- Color factor *q* vs. *g* Eloss diff interesting question (?)
- Ideas for *q/g* conversion already constrained by intermediate pt direct photon yield
- Direct photon spectrum hinting at some A+A modification
- shadowing/isospin effect supported by new 62.4 GeV data?
- Highlights better understanding of initial state effects even in hadron suppression
- Direct Photon-Jet and Heavy *q*-Jet Correlation measurements underway
- First measurements of both A+A consistent w/ expected suppression of -jet pairs
- Improvements in p+p and Run7 A+A should improve observation of A+A suppression of -jet pairs
- Also allow quark jet “tag”

## Backup

## Scan:  Shape Study

- With these, do systematic study of shape
- rms, kur (4th moment,  non-gaussianness), peak location D

- PHENIX

- Fit D

- Fix D

- Use Fit w/ allowing Away Peak

- PHENIX Work In Progress

- Away Width

## pT Dependence of shape

- Most interesting feature, here again is constant D

- PHENIX Final

- PHENIX

- This is expected in some “Mach Cone” explanations, but inconsistent with initial  color Cerenkov cone model...

## pT Dep. of Shape and Yields

- HS Ratio allows one to see where cone appears and “disappears”

- Detailed study of pT dep. in central Au+Au

- PHENIX

##  pT Dependence of Yields

- Calculate slope of the yields in each region
- S region:  harder than bulk
- New interpretation: H region harder than shoulder until quenched—then dominated by tails of S or bulk
- H region centrality dependence much like inclusive high pT suppression

- pT trig

- Centrality

- Inclusive *h*

## Cone Chemistry

- Triggering on high pT and identify the associated hadrons
- Cone shape observed baryons/mesons both (slight differences?)
- B/M Ratio btw bulk and jet

## Au+Au RP Dependence

- Is there any “path-length”, direction (wrt RP) dependence?
- Seems to be small, or hidden w/ RP reso.

## Cu+Cu RP Dependence

- Cu+Cu same eccentricity in smaller Npart range (also range where cone could be            distorting/disappearing)
- Still no major difference seen
- could still be RP resolution, even worse in Cu+Cu
- New RP detector in Run 7 Au+Au

- PHENIX Work in Progress

**Stony Brook Analysis (M. McCumber and JF)**

## Conclusions so far about the Cone

- Exists in ~all systems/ “hot medium” energies (including SPS!) and systems
- shape independent of centrality
- pT dependence is rich in physics:
- Cone location is ~independent of pt
- Slope of cone assoc. pt dependence of associated is like slightly harder than bulk, independent of trigger pt, ~centrality
- not shown (WIP): cone yield at fix assoc pt, weakly rises w/ trigger pt, slower than p+p jet
- B/M Ratio of Cone is lower than bulk, higher than pure jet

- Looking like jet-related medium excitation!

- These are consistent w/ some Mach Cone expectations

## Switching Gears (a little)

- Picture of direct photons being unmodified not completely valid especially at lower pt
- First direct porton from  Fragmentation/ Bremstrahlung  from jets ie suppressed
- However in addition, enhancement due to analagous mechanisms of the quenching jet-medium interactions
- Multiple Scattering (Collisions)
- Radiation

- Another type of Jet-Medium Interaction Signal!

**Notes:**
But besides

## Jet-Medium Photons

-  -jet Conversion
- Model: q jets traversing q/g bath convert (Kinematics: small *u* dominates:  *p**** ≈ p**q*)  First calc Fries, et. al./ more complete treatment w/ Turbide,Gale et. al.
- Fragmentation (Brems.) 
- Jet Eloss implies suppression of Frag  but Zakarov/others predict enhancement (New paper from E. Wang et. al.)  also included by the above authors.

- w/o suppresion

## Implications/Discussion

- Homework for theory:
- Bremstrahlung enhancement **must exist** (in however small amount) if gluon radiative Eloss (GLV, BDPMS...) is present
- can discrepancy be accounted for?  Another constraint on radiative picture?
-  g-jet conversion seems reasonable given a QGP, where does it go wrong? (modified S...)
- Interpretation of the partonic medium?
- Is there suppression in high pt direct?  Still need more precision at high pT

## PHENIX @ RHIC

- Central Arm

- Forward/Bkwd Muon Arms

- Central Arm