# Presentation: 571804

## If Quarkonia Could Talk

- Abigail Bickley
- Michigan State University
- August 9, 2007

- ??

- ??

## Quarkonia Questions

- Production Mechanism:
- Heavy quarks predominantly generated in hadronic collisions via gluonic diagrams
- Generation occurs during hard parton collisions early in the collision
- Details of hadronization process remain unclear
- Properties of Cold Nuclear Matter:
- Initial state energy loss
- Gluon shadowing
- Cronin
- Nuclear absorption
- Properties of Hot Nuclear Matter:
- Degree of in medium modification
- Relative influence of suppression mechanisms, recombination, feeddown & sequential melting

- Relative influence on yields
- needs to be determined

- Abigail Bickley, August 9, 2007

## J/ Production Mechanism

**J/******** Production Mechanism**

- Color Singlet Model:
- Color singlet cc pair created in same quantum state as J/
- Underpredicts J/ production cross section by a x10
- Predicts no polarization

- Abigail Bickley, August 9, 2007

## J/ Production Mechanism

**J/******** Production Mechanism**

- Color Singlet Model:
- NRQCD Color Octet Model:
- Includes octet state cc pairs that radiate soft gluons during hadronization
- Color octet matrix elements derived from experimental data were expected to be universal, but are not
- Predicts large transverse polarization (>0) at high pT that is not seen in experimental data

- Abigail Bickley, August 9, 2007

## J/ Production Mechanism

**J/******** Production Mechanism**

- Color Singlet Model:
- NRQCD Color Octet Model:
- Color Evaporation Model:
- Phenomenological approach
- Charmonium states formed in proportions determined by experimental data for any cc pair that has a mass below the DD threshold
- Uses emission of soft gluons to form J/
- Predicts no polarization

- Abigail Bickley, August 9, 2007

## J/ Production Mechanism

**J/******** Production Mechanism**

- Color Singlet Model:
- NRQCD Color Octet Model:
- Color Evaporation Model:
- pQCD involving 3-gluons:
- Hadronization mechanism includes channel involving the fusion of a symmetric color octet state with an additional gluon
- Successfully reproduces experimental cross section and polarization measurements
- Fails to reproduce experimental rapidity distribution => New result!

- Abigail Bickley, August 9, 2007

## In medium effects

- Color screening
- Suppression
- Recombination
- Sequential melting

- Abigail Bickley, August 9, 2007

## Color Screening & Suppression

- Color Screening:
- Color charge of one quark masked by the surrounding quarks
- Prevents cc binding in the interaction region
- Characterize by Debye screening radius (rD)
- If the screening radius is smaller than the J/ radius then the quarks are effectively masked from one another
- J/ Suppression Models:
- Heavy quarkonia are formed only during the initial hard nucleon-nucleon collisions
- Subsequent interactions only result in additional loss of yield

- Abigail Bickley, August 9, 2007

## Recombination

**Recombination**

- Recombination Models:
- In central heavy ion collisions more than one cc pair is formed
- RHIC: 10-40
- LHC: 100-200
- Regeneration of J/ pairs possible from independently produced c & c
- Leads to an enhancement of J/ yield (or less dramatic suppression)
- Results in modified rapidity and pT spectra
- Comments:
- On what time scale does this process occur?
- What is a reasonable path length to assume the quarks traverse to recombine?

- Abigail Bickley, August 9, 2007

## Sequential Melting

- Sequential Melting:
- J/ yield is populated from both direct production and feeddown from the higher resonance states
- Relative yield from each source experimentally found:
- 10% ’ feeddown, 30% c feeddown, 60% direct production
- Medium conditions determine whether each state is bound
- Recent lattice results => J/ suppression turns on at ??

- Abigail Bickley, August 9, 2007

## Deconfinement & the Lattice

**Deconfinement & the Lattice**

- Temperature dependence of screening radius shows no strong transition at Tc
- No significant reduction in  J/ mass or peak strength observed up to 1.5 Tc
- J/ suppression may not turn on until T > 2 Tc

- Abigail Bickley, August 9, 2007

## Deconfinement & the Lattice

**Deconfinement & the Lattice**

- Temperature dependence of screening radius shows no strong transition at Tc
- No significant reduction in  J/ mass or peak strength observed up to 1.5 Tc
- J/ suppression may not turn on until T > 2 Tc

- Quarkonium spectral functions calculated within a potential model with screening
- Provides description of quarkonium dissociation at high T
- Lattice data consistent with J/ dissolution just above Tc

- Mócsy & Petreczky,
- hep-ph/0705.2559

- Abigail Bickley, August 9, 2007

## Production Mechanism: p + p 

-  Allows testing of production mechanisms
-  Provides baseline measurement to which
-     all other collision systems can be compared

- Abigail Bickley, August 9, 2007

## J/ Cross Section vs Rapidity

**J/******** Cross Section vs Rapidity**

- Data now limited by systematic error not statistics
- The data appear flat over the rapidity range |y|<1.5
- mid and forward rapidity systematic errors are independent   a narrower distribution is not excluded.
**B****ll***** ********pp****(J/******** )=178±3± 53 ± 18 nb**

- Abigail Bickley, August 9, 2007

## J/ Cross Section vs Rapidity

- Khoze model inconsistent with the steepness of the slope at forward rapidity

- Abigail Bickley, August 9, 2007

## J/ Cross Section vs Rapidity

**J/******** Cross Section vs Rapidity**

- Comparison with theoretical predictions allows differentiation among the available J/ production mechanisms
- Many calculations are inconsistent with data

- Abigail Bickley, August 9, 2007

## Cold Nuclear Matter - p+A

- Used to disentangle initial state and nuclear medium effects

-  nuclear absorption
-  energy loss
-  etc.

-  shadowing
-  anti-shadowing
-  gluon saturation

- Abigail Bickley, August 9, 2007

## Cold Nuclear Matter @ SPS: p+A

**Cold Nuclear Matter @ SPS: p+A**

-   Trend in data reproduced well by Glauber calculation
-   Calculation assumes reduction in yield is purely a result of
-      final state absorption in cold nuclear matter

- Abigail Bickley, August 9, 2007

## Cold Nuclear Matter @ RHIC- d+Au

**Cold Nuclear Matter @ RHIC- d+Au**

- Absorption of J/ by nuclear matter
- Modification of PDF due to gluon shadowing

- PHENIX data compatible with:
-   weak gluon shadowing
-   weak absorption : 1 mb (max 3mb)

**Vogt, PRC71, 054902 (2005)****, ****Kopeliovich, NP A696, 669 (2001) **

- PHENIX PRL 96, 012304 (2006)

- Data

- Abigail Bickley, August 9, 2007

## Heavy Ion Collisions

-  In Medium Modification
-  Color Screening
-  Recombination
-  Sequential Melting

- Abigail Bickley, August 9, 2007

## NA50 Pb+Pb

-  Plot ratio of cross sections from  J/ and Drell-Yan:
- identical experimental biases,
- 	inefficiencies,
- 	selection criteria,
- 	analysis cuts
-  Normal Nuclear Absorption:
-   p+A data at 450 and 400 GeV
-   S-U at 200 GeV
-   abs = 4.2 ± 0.4 mb

- Eur.Phys.J. C39, 335 (2005)

- Abigail Bickley, August 9, 2007

## NA50 Pb+Pb

**NA50 Pb+Pb**

-  Plot ratio of cross sections from  J/ and Drell-Yan:
- identical experimental biases,
- 	inefficiencies,
- 	selection criteria,
- 	analysis cuts
-  Normal Nuclear Absorption:
-   p+A data at 450 and 400 GeV
-   S-U at 200 GeV
-   abs = 4.2 ± 0.4 mb
- Summary:
- 	Ratio is “normal” for peripheral collisions, but becomes more and more “abnormal” with increasing centrality

- Eur.Phys.J. C39 (2005) 335-345.

- Abigail Bickley, August 9, 2007

## NA60 In+In 

**NA60 In+In **

- Consistent agreement between In+In and Pb+Pb
-  J/ suppression beyond that expected from a Glauber calculation of final state absorption in cold nuclear matter based on NA50 p+A data
- Future results will show rapidity and pT dependence of production

- Abigail Bickley, August 9, 2007

## Forward Rapidity @ RHIC

**Forward Rapidity @ RHIC**

- Smooth suppression with increasing collision centrality
- Good agreement between Cu+Cu and Au+Au in region of overlap

- (Cu+Cu)

- Vogt *et al*., nucl-th/0507027

- Abigail Bickley, August 9, 2007

## Mid-Rapidity @ RHIC

**Mid-Rapidity @ RHIC**

- Smooth suppression with increasing collision centrality
- Reasonable agreement between Cu+Cu and Au+Au in region of overlap
- Final Cu+Cu coming soon

- (Cu+Cu)

- Vogt *et al*., nucl-th/0507027

- Abigail Bickley, August 9, 2007

## J/ dissociation by hadronic and partonic comovers
Data: forward rapidity more suppressed than mid-rapidity
Theory: opposite!

- J/ dissociation by hadronic and partonic comovers
- Data: forward rapidity more suppressed than mid-rapidity
- Theory: opposite!

- J/ dissociation via thermal gluons
- Data: weaker degree of suppression than theory

**RHIC Suppression**

- Abigail Bickley, August 9, 2007

## SPS & RHIC Comparison

**SPS & RHIC Comparison**

- Similar level of suppression:
- 200 GeV Au+Au @ |y|<0.35
- 158 GeV/A Pb+Pb @ 0<y<1

- Bar: uncorrelated error
- Bracket : correlated error

- Abigail Bickley, August 9, 2007

## SPS & RHIC Comparison

**SPS & RHIC Comparison**

- NA50  & PHENIX (|y|<0.35)
- 	Statistically _consistent_ degree of suppression
- PHENIX Mid & Forward y
- 	Statistically _INconsistent_ degree of suppression

- Abigail Bickley, August 9, 2007

## Recombination @ RHIC?

-  Recombination can account for the suppression level
-  However, so can a reduced temperature
-  Model highly dependent on input parameters

- Abigail Bickley, August 9, 2007

## Recombination @ RHIC?

- Recombination predicts a narrower rapidity distribution with an increasing Npart

- Data shows only a slight narrowing

- Thews & Mangano, Phys.Rev. C73 (2006) 014904.

- No Recombination
- Recombination

**PRL98, 232301 (2007)**

- Abigail Bickley, August 9, 2007

## Data: 
Tapers off at ~0.6
Insufficient to establish existence of plateau
Need higher energy densities

- Data:
- Tapers off at ~0.6
- Insufficient to establish existence of plateau
- Need higher energy densities

**Sequential Melting @ SPS?**

- Theory Expectation:
-  step behavior as each state melts
-  plateau in survival probability at
-     ~60% for T<Tdis(J/)

- Abigail Bickley, August 9, 2007

## Data: 
No evidence this 
behavior @ RHIC

- Data:
- No evidence this
- behavior @ RHIC

**Sequential Melting @ RHIC?**

- Theory Expectation:
-  step behavior as each state melts
-  plateau in survival probability at
-     ~60% for T<Tdis(J/)

- Abigail Bickley, August 9, 2007

## Future RHIC Measurements

- PHENIX Capabilities for J/ flow from Run7

- Tony Frawley

- Projected Statistical Capabilities
- PHENIX, Au+Au Run 7, 0.77/nb

- Abigail Bickley, August 9, 2007

## The Quarkonia Message

- Production Mechanism:
- Color Singlet Model
- NRQCD Color Octet Model
- Color Evaporation Model
- pQCD involving 3-gluons
- Cold Nuclear Matter:
- NA50 p+A: reduction in yield is a result of final state absorption
- PHENIX d+Au: consistent with weak shadowing and absorption
- Hot Nuclear Matter:
- SPS: suppression in excess of final state nuclear absorption
- RHIC: suppression beyond CNM, but consistent with SPS!
- Recombination: could potentially explain suppression versus centrality, _BUT_ must also be consistent with rapidity and pT spectra
- Sequential Melting: melting temperature of J/ must be resolved

- Comprehensive interpretation needed!

- Abigail Bickley, August 9, 2007

## Backup

- Abigail Bickley, August 9, 2007

## Future RHIC Measurements

**Future RHIC Measurements**

- Abigail Bickley, August 9, 2007

## <pT2> extracted using Kaplan function integrated to 

Mid-rapidity:

Forward rapidity:	

If the exponent is allowed to float a slightly better fit is obtained, 2/ndf = 20/16
But the <pT2> is not significantly modified: <pT2> = 3.68

- <pT2> extracted using Kaplan function integrated to 
- Mid-rapidity:
- Forward rapidity:
- If the exponent is allowed to float a slightly better fit is obtained, 2/ndf = 20/16
- But the <pT2> is not significantly modified: <pT2> = 3.68

**J/******** Cross Section vs p****T**

- Abigail Bickley, August 9, 2007

## Ratio of pT spectra

**Ratio of p****T**** spectra**

- Significant decrease observed in ratio of |y|<0.35 and 1.2<|y|<2.2 pT spectra
- Indicates forward rapidity pT spectrum is softer than mid-rapidity
- At forward rapidity longitudinal momentum increased  less energy is available in the transverse direction

- PRL 98, 232002 (2007)

- Abigail Bickley, August 9, 2007

## J/ Cross Section vs Energy

**J/******** Cross Section vs Energy**

- Consistent with trend of world’s data and with the COM
- but unable to differentiate between PDF’s

- Abigail Bickley, August 9, 2007

## <pT2> vs Collision Energy

- PHENIX <pT2 > measurements compared to measurements at other energies.
- As a function of collision energy the data show a linear dependence on the ln(√s).

- Abigail Bickley, August 9, 2007

## Cold Nuclear Matter @RHIC - d+Au

**Cold Nuclear Matter @RHIC - d+Au**

- RdAu

- Weak absorption
- Weak shadowing

- PHENIX, PRL96, 012304 (2006)
- Klein & Vogt, PRL91, 142301 (2003)

- Abigail Bickley, August 9, 2007

## <pT2> versus Centrality

**<p****T****2****> versus Centrality**

- Good consistency is found between the <pT2> in Heavy Ion collisions as a function of centrality and the p+p results for the <pT2> integrated over pT < 5GeV/c where Heavy Ion data exists.

- Abigail Bickley, August 9, 2007

## PHENIX Detector: Muon Arms

**PHENIX Detector: Muon Arms**

- Event Mixed
- Background
- Subtraction

- J/  + -
- p > 2GeV/c
-  1.2 < |y| < 2.2
-  

- Abigail Bickley, August 9, 2007

## PHENIX Detector: Central Arms

**PHENIX Detector: Central Arms**

- Like Sign
- Subtraction

- J/  e+ e-
- p > 0.2GeV/c
-  || < 0.35
-  

- Abigail Bickley, August 9, 2007