# Presentation: 479647

## News  from PHOBOS

- Gunther Roland/MIT

**2003 Conference on**
** ****Intersections of Particle and Nuclear Physics**

***a first look at d+Au p******T****** spectra***

##                   Collaboration (May 2003)

- Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Bruce Becker, Russell Betts,
- Abigail Bickley, Richard Bindel, Andrzej Budzanowski, Wit Busza (Spokesperson), Alan Carroll,
- Patrick Decowski, Edmundo Garcia, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen,
- Stephen Gushue, Clive Halliwell, Joshua Hamblen, Adam Harrington, Conor Henderson,
- David Hofman, Richard Hollis, Roman Holynski, Burt Holzman, Aneta Iordanova, Erik Johnson,
- Jay Kane, Nazim Khan, Piotr Kulinich, Chia Ming Kuo, Jang Woo Lee, Willis Lin, Steven Manly,
- Alice Mignerey, Gerrit van Nieuwenhuizen, Aaron Noell, Rachid Nouicer, Andrzej Olszewski,
- Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Louis Remsberg, Christof Roland,
- Gunther Roland, Joe Sagerer, Pradeep Sarin, Pawel Sawicki, Iouri Sedykh, Wojtek Skulski,
- Chadd Smith, Peter Steinberg, George Stephans, Andrei Sukhanov, Ray Teng,
- Marguerite Belt Tonjes, Adam Trzupek, Carla Vale, Robin Verdier, Gábor Veres, Bernard Wadsworth, Frank Wolfs,  Barbara Wosiek, Krzysztof Wozniak, Alan Wuosmaa, Bolek Wyslouch, Jinlong Zhang
- 	ARGONNE NATIONAL LABORATORY	BROOKHAVEN NATIONAL LABORATORY
- 	INSTITUTE OF NUCLEAR PHYSICS, KRAKOW	MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- 	NATIONAL CENTRAL UNIVERSITY, TAIWAN	UNIVERSITY OF ILLINOIS AT CHICAGO
- 	UNIVERSITY OF MARYLAND	UNIVERSITY OF ROCHESTER

## PHOBOS Detector in 2002

**1m**

**ZDC**

**ZDC**

## pT Distribution of Charged Particles

- Systematic Errors not shown

- Phobos Preliminary

**p****T**** Distribution of Charged Particles**

## pT Spectra for Au+Au @ 200 GeV

**p****T**** Spectra for Au+Au @ 200 GeV**

**0.2<y************<1.4**

**nucl-ex/0302015**
**Submitted to Phys Lett B**

- 344 ± 12

- 276 ± 9

- 200 ± 8

- 138 ± 6

- 93 ± 5

- 65 ± 4

**N****part**

- 0-6%

- 6-15%

- 15-25%

- 25-35%

- 35-45%

- 45-50%

**Centrality**

**Centrality range:**
** ****<b> from 10 to 3 fm**
** ****<********> from 3 to 6**

## Ratio of Au+Au and pp spectra at 200 GeV

**mid-peripheral**

**central**

**N****part**** = 65 ± 4**

**N****part**** = 344 ± 12**

**Strong modification of spectral shape relative to pp**
**already in mid-peripheral events**
**Strong violation of expected N****coll**** scaling**
**Jet quenching?**
**Initial state Gluon Saturation?**

## ok, so let’s look at d+Au....

**ok, so let’s look at d+Au....**

## This Year: PHOBOS Detector 2003

**This Year: PHOBOS Detector 2003**

-  Moved TOF walls back ~ 5 m from interaction point

-  Installed new spectrometer trigger detector that selects on high pT tracks

-  Installed new “time-zero” (T0) Cerenkov detectors to provide triggering and on-line vertexing as well as a start time for our TOF walls.

-  Proton calorimeter on Gold and Deuteron “going” sides for dA run

- SPECTRIG

- mini-pCal

- pCal

## Spectrometer Trigger

**Scintillator **
**hodoscopes  **
**(45****o**** and 90****o****)**

**ToF walls**
** ****(45****o**** and 90****o****) **

** ****Select events with particle hitting ToF wall**
** ****Enhance high-p****T**** (straight) tracks: “online” tracking**
** ****Decision made in 50 ns**

**rejected**

**accepted**

## Reminder: Centrality in Au+Au

**Data**

**Paddle signal**

**Data+MC**

** ****HIJING +GEANT**
** ****Glauber calculation**
** ****Model of paddle trigger**

**Paddle: Multiplicity in 3 < |********| < 4.5**

## Centrality determination in d+Au

**HIJING d+Au MC**

**Centrality in d+Au: Handle with care!**

## Preliminary Results from d+Au

## Preliminary Results from d+Au

**Preliminary Results from d+Au**

## Reminder:  Au+Au/pp at 200 GeV

**mid-peripheral**

**central**

**N****part**** = 65 ± 4**

**N****part**** = 344 ± 12**

## Preliminary Results from d+Au

## Summary

**Successful run of upgraded Detector**
**Forward Proton calorimeter**
**Spectrometer Trigger**
**Online vertex Trigger.**
**First Look: Centrality dependence of d+Au p****T**** spectra**
**Resemble p+A fixed target data**
**Very different from Au+Au**
**Much more to come**
**4-******** dN/d******
**PID spectra, ratios**
***?***