# Presentation: 350408

## Particle Production at Very Low and Intermediate Transverse Momenta in d+Au and Au+Au Collisions

**Particle Production at Very Low and Intermediate Transverse Momenta in d+Au and Au+Au Collisions**

**Adam Trzupek**
***The Henryk Niewodniczański Institute of Nuclear Physics***
***Polish Academy of Sciences***
*** ******Kraków, Poland****** ***

***Quark Matter 2005***
***18th International Conference on Ultra-Relativistic ***
***Nucleus-Nucleus Collisions, Budapest, Hungary***

##                 Collaboration (August 2005)

- Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Richard Bindel,
-  Wit Busza (Spokesperson), Zhengwei Chai, Vasundhara Chetluru, Edmundo García, Tomasz Gburek,
- Kristjan Gulbrandsen, Clive Halliwell, Joshua Hamblen, Ian Harnarine, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Jay Kane,Piotr Kulinich,
- Chia Ming Kuo,  Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey,
- Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed,
- Eric Richardson, Christof Roland, Gunther Roland, Joe Sagerer, Iouri Sedykh, Chadd Smith,
- Maciej Stankiewicz, Peter Steinberg, George Stephans, Andrei Sukhanov, Artur Szostak,
- Marguerite Belt Tonjes, Adam Trzupek, Sergei Vaurynovich, Robin Verdier, Gábor Veres,
- Peter Walters, Edward Wenger, Donald Willhelm, Frank Wolfs,  Barbara Wosiek, Krzysztof Woźniak,
- Shaun Wyngaardt, Bolek Wysłouch
- 	ARGONNE NATIONAL LABORATORY	BROOKHAVEN NATIONAL LABORATORY
- 	INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW	MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- 	NATIONAL CENTRAL UNIVERSITY, TAIWAN	UNIVERSITY OF ILLINOIS AT CHICAGO
- 	UNIVERSITY OF MARYLAND	UNIVERSITY OF ROCHESTER

##  Particle Production at Very Low pT

** ****Particle Production at Very Low p****T**

***Enhanced production of low-p******T****** particles was predicted as       a consequence of NEW long wave-length phenomena***

**PHOBOS experiment has a unique capability to measure particles down to very small transverse momenta: **
**0.03 - 0.2 GeV/c **

**    ****Au+Au, 200 GeV**
**    ****centrality: 0-15%**
**    ****mid-rapidity**
**PHOBOS:**
****** ****PRC 70 (2004) 051901(R)  **
****** ****PLB 578 (2004) 297**

**TAIL**

**BULK**

***Particle spectra at low p******T****** can be modified due to collective transverse expansion***

**A recent optical model implies that chiral symmetry restoration can have significant impact on shapes of pion spectra at very low p****T**
***J.Cramer, et al., Phys.  Rev. Lett.  94 (2005) 102302***

## pT and PID Measurement in PHOBOS Spectrometer

**10 cm**

**PHOBOS Spectrometer**
-  **16 layers of silicon wafers**
** ****fine pixelization, precise dE measurement**
** ****collision vertex close to spectrometer**
** ****near mid-rapidity coverage**
** ****dipole magnetic field of 2T at maximum**

**70 cm**

## PHOBOS PID Capabilities

**p****T ****(GeV/c)**

**0.03**

**0.5**

**5.0**

**Stopping**
**particles**

**dE/dx**

**TOF**

**E****loss**** ****(MeV)**

**PHOBOS PID Capabilities**

**1/v (ps/cm)**

**PRC 70 (2004) 051901(R)**

**p+p**

******+****+********-**

**p (GeV/c)**

## Identified Particle pT -Spectra, Au+Au at 62.4 GeV

**Identified Particle ****p****T**** -Spectra,**** Au+Au at 62.4 GeV**

**These results at 62.4 GeV fit smoothly into the energy evolution of antiparticle/particle ratios**

## Low-pT  Spectra of Identified

**Particles in  Au+Au Collisions **
**at ********s****N****N**** =****62.4 GeV**

**Blast wave fit parameters:**
**  ****0-15%: T****fo ****= 99 MeV, <********T****>=0.51 c**
**15-30%: T****fo ****= 98 MeV, <********T****>=0.51 c**
**30-50%: T****fo ****= 97 MeV, <********T****>=0.49 c**

**(****2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****] **

**(****2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****] **

**(****2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****] **

## Low-pT Spectra of Identified Particles  Au+Au at sNN  = 200 GeV

**Low-p****T**** Spectra of Identified Particles **** Au+Au ****at ********s****NN  ****= 200 GeV**

** ****No enhancement in low****-****p****T**** yields for pions is observed **
** ****Flattening of (p+p) spectra down to very low p****T****, consistent**
** ****with transverse expansion of the system**

**PHOBOS, PR C70, 051901 (R) (2004) PHENIX, PR C69, 034909 (2004)**

**Blast Wave Fit:**
**               ****T****fo****= 99 MeV **
**                 ****<********T****> = 0.54 c**

**T= 229 MeV for  (********+****+********-****) **
**      ****293 MeV for (K****+****+ K****-****) **
**      ****392 MeV for (p + p) **

**B-E fit**

**BWF fit**

**(****2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****] **

## Invariant Yields of Very Low pT Particlesin Central Au+Au Collisions at sNN=200 GeV

**(****2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****] **

**Invariant Yields of Very Low p****T ****Particles****in Central Au+Au Collisions at ********s****NN****=200 GeV**

**(****2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****] **

## Low-pT Spectra as Model Constraints

**J. Cramer (private comm.,**
**erratum to be published)**

**J.Cramer, et al., **
**PRL 94 (2005) 102302**

**(****2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****] **

## Identified Particle pT -Spectra, d+Au at sNN= 200 GeV

**Identified Particle p****T ****-Spectra,**** d+Au at ********s****NN****=**** 200 GeV**

**p****T**** range:**
- (******+**+******-**) :  > 0.03 GeV/c
- (K++ K-): > 0.09 GeV/c
- (p + p)  : > 0.14 GeV/c
** ****Background corrections:**
-    very low-pT:
- 	(******+**+******-**) :  20%
- 	(K++ K-): 10%
- 	(p + p)  : 20%
-    intermediate pT
- 	(p + p)  : ~20%
**Systematic uncertainties:**
-   very low pT:  ~30%
-   intermediate pT : ~15%
**Event selection:**
-   described in PRL 93, 082301

**T****fo ****= 152 GeV, <********T****>=0.37 c**

**(****2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****] **

## mT -Scaling in d+Au at sNN= 200 GeV

**m****T**** -Scaling in d+Au at ********s****NN****=**** 200 GeV**

**(********+****+********-****),  (K****+****+ K****-****), (p + p)  **
**m****T****-yields are similar after scaling (K****+****+ K****-****) yield by a factor 2 (strangeness suppression)**
**Local slopes of m****T**** -spectra similar**

**T****loc****[****GeV/c****2****]**

## mT -Scaling in d+Au vs. Au+Au at sNN = 200 GeV

**m****T**** -Scaling in d+Au vs. Au+Au at ********s****NN ****=**** 200 GeV**

**PRC 70 (2004) 051901(R)**

**In central Au+Au, larger flattening for of p+p m****T**** spectra at small p****T**** **
**Low-p****T**** spectra of p+p can constrain models describing collective transverse expansion of the system**

**(2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****]**** **

**(2********p****T****)********1****d****2****N/dydp****T****[c****2****/GeV****2****]**** **

**T****loc****[GeV/c****2****]**

**T****loc****[GeV/c****2****]**

## Summary

** ****No evidence for enhanced production of very low-p****T**** pions  ****iaii****in the most****i****central Au+Au collisions at energy 62.4 and  ****iaii****200 GeV**
**  ****Flattening of p+p m****T**** spectra at low-p****T ****in 15% most central **** ****iaii****Au+Au collisions at energy 62.4 and 200 GeV**
**  ****Approximate m****T**** scaling of particle spectra for d+Au  ****iaii****collisions at low and intermediate transverse momentum **
**  ****New constraints on models and fits **