Carl Gagliardi -- Forward and p+A 1

RHIC II Forward and p+A PWG

Mike Leitch

Kirill Tuchin

Carl Gagliardi

http://www.phenix.bnl.gov/phenix/WWW/publish/leitch/rhicii-forward/rhicii-forward.html

Carl Gagliardi -- Forward and p+A 2

Workshop Program

• STAR Forward Meson Spectrometer – Les Bland• Small-x Theory Overview – Yuri Kovchegov• Heavy-quark rates – Tony Frawley• Forward-tagged Drell-Yan (and other signals) – Jen-

Chieh Peng• PHENIX Endcap Silicon Vertex Detector – Pat

McGaughey• Ultra-peripheral Physics at Forward Angles – Tony Baltz• Forward Physics with R2D – Peter Steinberg• Forward Light Hadrons – Ramiro Debbe• (PHENIX Nosecone Calorimeter)

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Rcp ratios (from BRAHMS) At At =0 the =0 the central events central events have the ratio have the ratio systematically systematically above that of above that of semi-central semi-central events. We see events. We see a reversal of a reversal of behavior as we behavior as we study events at study events at =3.2=3.2

Rcp

1/<Ncoll central> NABcentral(pT,

1/<Ncoll periph> NAB

periph(pT,)

Carl Gagliardi -- Forward and p+A 4

Also RCP from PHENIX and RdAu from STAR

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Our Model

from D. Kharzeev, Yu. K., K. Tuchin, hep-ph/0405045, where we construct a model based on above physics + add valence quark contribution

RdAu

pT

pT

RCP

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Back-to-back CorrelationsAn interesting process to look at is when one jet is at forwardrapidity, while the other one is at mid-rapidity:

from Kharzeev, Levin, McLerran, hep-ph/0403271

The evolution between the jetsmakes the correlations disappear:

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Fixed as

E & pT grows

Large 0+h± correlations • Suppressed at small <xF> , <pT,>

Consistent with CGC picture

•Consistent in d+Au and p+p at larger <xF>

and <pT,>

More data are needed…Statistical errors only

25<E<35GeV

35<E<45GeVSTAR

Preliminary

dAu Correlations: probing low x

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Is hydro just good at the “sweet spot”(midrapidity @ top energies) or is

there a broader systematic?

PHOBOS v2 vs. η

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Limiting Fragmentation (in PHOBOS and elsewhere)

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Unique Aspects of RHIC

• Transition from the unsaturated to the saturated state

• (and as Larry noted: It’s good to be first)

• Polarized p+A at a collider

• But does polarization win us anything?!?

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Other Important Questions to Address in the Forward Region

• Heavy-ion reaction dynamics

• Gluon density in heavy nuclei

• Nucleon and meson structure (in p+p and p+d collisions)– Tagged J/Ψ– Tagged Drell-Yan– …..

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Additional Homework Assignments

• Rate estimates for realistic RHIC II luminosities (especially for Drell-Yan and forward tagged J/Ψ and Drell-Yan)

• What are all the trade-offs between d+A vs. p+A ?

• When will p+A run at the LHC ?