m. j. tannenbaum brookhaven national laboratory upton, ny 11973 usa

BNL-Seminar-Dec 7, 2004 M. J. Tannenbaum 1/54

From Bjorken Scaling to pQCD---From Bjorken Scaling to pQCD---Experimental techniques from p-p Experimental techniques from p-p

collisions of the 1970’s with application to collisions of the 1970’s with application to Au+Au collisions at RHICAu+Au collisions at RHIC

M. J. TannenbaumBrookhaven National Laboratory

Upton, NY 11973 USANuclear Physics Seminar

Physics Department, BNL December 7, 2004


Bjorken Scaling in Deeply Inelastic Bjorken Scaling in Deeply Inelastic Scattering and the Parton Model---1968Scattering and the Parton Model---1968

€

ν =Q2

2Mx

Phys. Rev. 179, 1547 (1969)

Phys. Rev. 185, 1975 (1969)


BBK 1971BBK 1971S.M.Berman, J.D.Bjorken and J.B.Kogut, Phys. Rev. D4, 3388 (1971)

• BBK calculated for p+p collisions, the inclusive reaction A+B C + X when particle C has pT>> 1 GeV/c

• The charged partons of DIS must scatter electromagnetically “which may be viewed as a lower bound on the real cross section at large pT.”


CCR at the CERN-ISRCCR at the CERN-ISRDiscovery of high pDiscovery of high pTT production in p-p production in p-p

• e-6pT breaks to a power law at high pT with characteristic s dependence• Large rate indicates that partons interact strongly (>> EM) with other.• Data follow BBK scaling but with n=8!, not n=4 as expected for QED

F.W. Busser, et al., CERN, Columbia, Rockefeller Collaboration Phys. Lett. 46B, 471 (1973)

Bj scaling BBK scaling


BBK scaling with n=8, not 4 BBK scaling with n=8, not 4 Inspires Constituent Interchange ModelInspires Constituent Interchange Model

Berman, Bjorken, Kogut, PRD4, 3388 (1971)

xT=2pT/s

n=4 for QED or vector gluon

n=8 for quark-meson scattering by the exchange of a quark

CIM-Blankenbecler, Brodsky, Gunion, Phys.Lett.42B,461(1972)


State of the Art State of the Art Fermilab 1977Fermilab 1977

D. Antreasyan, J. Cronin, et al., PRL 38, 112 (1977)

Beautiful xT scaling at all 3 fixed target energies with n=8Totally Misleading--Not CIM or QCD but kT


CCOR 1978--Discovery of CCOR 1978--Discovery of “REALLY high p“REALLY high pTT>7 GeV/c” at ISR>7 GeV/c” at ISR

CCOR A.L.S. Angelis, et al, Phys.Lett. 79B, 505 (1978)See also A.G. Clark, et al Phys.Lett 74B, 267 (1978)

• Agrees with CCR, CCRS (Busser) data for pT < 7 GeV/c.

• Disagrees with CCRS fit pT > 7 GeV/c

• New fit is:


n(xn(xTT, , s) WORKS ns) WORKS n5=45=4++++

Same data Ed3/dp3(xT) ln-ln plot

QCD: Cahalan, Geer, Kogut, Susskind, PRD11, 1199 (1975)


ISR Expt’s more interested in n(xISR Expt’s more interested in n(xTT,,s) s) than absolute cross sectionthan absolute cross section

cross sections vary by factor of 2

Athens BNL CERN Syracuse Collaboration, C.Kourkoumelis, et al Phys.Lett. 84B, 279 (1979)

But n(xT,s) agrees


Status of ISR single particle Status of ISR single particle measurements 1978measurements 1978

kT is what made n=4++ n=8


Status of QCD Theory in 1978Status of QCD Theory in 1978


LO-LO-QQCCDD in 1 sli in 1 sliddee

A

B

ab

c

d

C

€

faA (x1) D cC /

€

fbB (x2) D dD /

€

dσdˆ t X


QQCCDD and Jets and Jets are now a cornerstone of the standard modelare now a cornerstone of the standard model

• Incredibly at the famous Snowmass conference in July 1982, many if not most people were skeptical

• The International HEP conference in Paris, three weeks later, changed everything.


THE UA2 Jet-Paris 1982THE UA2 Jet-Paris 1982From 1980--1982 most high energy physicists doubted jets existed because of the famous NA5 ET spectrum which showed NO JETS. This one event changed everybody’s opinion.


CCOR Jets after 8 orders of mag. PL 126B, 132 (1983)

Also Paris 1982-Jets in EAlso Paris 1982-Jets in ETT distribution distribution

1980 ICHEP-NA5 No Jets 7 orders of magnitude


DATA: CCOR NPB 209, 284 (1982)

Also Paris1982-first measurement of QCD Also Paris1982-first measurement of QCD subprocess angular distribution using subprocess angular distribution using 00--

00 correlations correlations

QQCCDD


The leading-particle effect a.k.a. trigger biasThe leading-particle effect a.k.a. trigger bias• Due to the steeply falling power-law spectrum of the scattered partons, the inclusive particle pT spectrum is dominated by fragments biased towards large z. This was unfortunately called trigger bias by M. Jacob and P. Landshoff, Phys. Rep. 48C, 286 (1978) although it has nothing to do with a trigger.

Fragment spectrum given pTq

Fragment spectrum given pT


<z<ztrigtrig> measured at ISR> measured at ISR

• <ztrig> ~ 0.8-0.9 at ISR, n~ 11

• <ztrig> xT scales

DATA: CCOR NPB 209, 284 (1982)

pTjet=pTtrig+1.5px

0.3 GeV/c<pT || <0.7 ||< 60o

ztrig=pTtrig/pTjet


How everything you want to know about JETS How everything you want to know about JETS was measured with 2-particle correlationswas measured with 2-particle correlations

CCOR, A.L.S.Angelis, et al Phys.Lett. 97B, 163 (1980) PhysicaScripta 19, 116 (1979)

pTt > 7 GeV/c vs pT

xE pTt

pout=pT sin

pTt pT


kkTT is not a parameter, it can be measured is not a parameter, it can be measured


Feynman Feynman Field & FoxField & Fox to the rescue to the rescue


• jT is parton fragmentation transverse momentum

• kT is transverse momentum of a parton in a proton (2 protons)

• xE=-pTpTt/|pTt|2 represents away jet fragmentation z

• pout is component of away pT perpendicular to trigger pTt

jjTT, k, kTT, x, xEE, p, poutout definitions all definitions all in plane transverse to beam directionin plane transverse to beam direction

pout2 =xE22 kTy 2 + jTy 2+ jTy 2

xE pTt

pout=pT sin

pTt pT


xxEE distribution measures fragmentation fn. distribution measures fragmentation fn.

xE ~ z/<ztrig>

Dq(z)~e-6z

• independent of pTt

<ztrig>=0.85 measured*

* but we did learn something new on this issue in PHENIX.

See M. Jacob’s talk EPS 1979 Geneva


CCOR <|pCCOR <|poutout|>|>22 vs x vs x22EE

pout2 =xE22 kTy 2 + jTy 2+ jTy 2

CCOR, A.L.S.Angelis, et al Phys.Lett. 97B, 163 (1980)


jjTT is constant-independent of p is constant-independent of pTtTt and and s s Characteristic of jet fragmentationCharacteristic of jet fragmentation

• it took the e+ e-

people several more years to get this correct---because they didn’t understand the seagull effect: (jT < pT)


kkTT varies with p varies with pTtTt and and s--not intrinsics--not intrinsic


We did (re)learn a few things at RHICWe did (re)learn a few things at RHIC• FFF’s formula was really:

• Jan Rak discovered this by insisting to rederive all the formulas, but it was in FFF’s paper. •<zt> depends on pTa as well as pTt but may be too confusing for this talk

pout2 =xE22 kTy zt 2 + jt

Ty 2+ jaTy 2

CCOR NPB 209, 284 (1982)


kkTT Phenomenology-I Phenomenology-I


kkTT Phenomenology-II Phenomenology-II

L.Apanasevich, et al, PR D59 074007 (1999)


Early theoretical attempt to understand kEarly theoretical attempt to understand kTT

• Modern work falls under the subject “resummation”

<kT>=3.5/2=2.5 GeV/c


Nicely covered in L.Apanasevich, et al, PR D59 074007 (1999), covered here for convenience and completeness

Gaussian Integrals-IGaussian Integrals-I


Gaussian Integrals--IIGaussian Integrals--II


Conclusions from ISRConclusions from ISR


A puzzle from RHIC: why does A puzzle from RHIC: why does NLO-QCD fit the p-p NLO-QCD fit the p-p 00 spectrum with no k spectrum with no kTT??

Data: PHENIX PRL 91, 241803 (2003)

Theory: W.Vogelsang, see B.Jager, A.Schafer, M.Stratmann,W.Vogelsang PRD67,054005(2003)


kkTT and NLO are distinct---e.g. Drell Yan and NLO are distinct---e.g. Drell Yan

A.S.Ito, et al, PRD23,604 (1981)Note Gaussian shape, no power-law tail!

J.K.Yoh, et al, CFS, PRL 41, 684 (1978)

A.L.S.Angelis, et al, CCOR, PLB 87, 398 (1979)


<p<pTT>(=>(=2k2kTT) vs ) vs s in Drell-Yans in Drell-YanCMOR, NPB348, 1 (1991)


N.B.-- Lots of Drell-Yan Measurements N.B.-- Lots of Drell-Yan Measurements at Colliders: all you need is luminosity.at Colliders: all you need is luminosity.

ISR CDF


kkTT and NLO II and NLO II

``Every final state in hard scattering carries the imprint of QCD dynamics at all scales.’’

• For the only measurement of kT in direct photon production that I know of, see UA2 Collaboration, ZPC 41, 395 (1988)

• They also measure cos* distribution for + Jet production and show that it is flatter than Jet+Jet (Compton-like).

• L.Apanasevich, et al, PR D59 074007 (1999) doesn’t measure kT they derive it by kT-smearing NLO cross predicitons to agree with measurements. See also hep-ex/0407011.

In George Sterman’s words 12/3/04:In George Sterman’s words 12/3/04:


Application to RHICApplication to RHIC


RHIC pp spectra RHIC pp spectra s=200 GeV s=200 GeV nicely illustrate hard scattering phenomenologynicely illustrate hard scattering phenomenology

0

• Good agreement with NLO pQCD

this is no surprise for `old timers’ (like me) since as I just explained,

single particle inclusive spectra were what proved QCD in the late 1970’s

before jets.

• Reference for A+A and p+A spectra 0 measurement in same experiment allows us the study of nuclear effect with

less systematic uncertainties.

PHENIX (p+p) PRL 91, 241803 (2003)

Hard Scattering -- varies with s

p-p

Thermally-shaped Soft Production: e-6pT indep.

s


Inclusive single hadron high pInclusive single hadron high pTT spectra in p-p all spectra in p-p all ss


xxTT scaling in p-p collisions x~0.05-0.10 scaling in p-p collisions x~0.05-0.10

xT


-A DIS at AGS (1973)--Hard-Scattering is pointlike -A DIS at AGS (1973)--Hard-Scattering is pointlike

M. May, et al, (M.Murtagh, T.Kirk, MJT) PRL 35, 407 (1975)


M. May, M. May, et al.,et al.,


High pHigh pTT in A+B collisions--- in A+B collisions---TTABAB Scaling Scaling

view along beam axis

• For point-like processes, the cross section in p+A or A+B collisions compared to p-p is simply proportional to the relative number of pointlike encounters

A for p+A, AB for A+B for the total rate

TAB the overlap integral of the nuclear profile functions, as a function of impact parameter b

looking down


What really Happens: for p+A RWhat really Happens: for p+A RAA > 1! > 1! The anomalous nuclear enhancement a.k.a. the Cronin effect--due to multiple scattering of initial nucleons (or constituents)

•Known since 1975 that yields increase as A, > 1

•J.W. Cronin et al.,Phys. Rev. D11, 3105 (1975)•D. Antreasyan et al.,Phys. Rev. D19, 764 (1979)

=1.150.01


For A+A: RFor A+A: RAAAA1 before RHIC1 before RHIC

• The importance of comparison data!


RRAA AA at RHIC--at RHIC--Suppression to at least 10 GeV/cSuppression to at least 10 GeV/c

PHENIX, PRL 91 (2003) 072301

Binary scaling

Participant scaling

Factor 5

Large suppression in central AuAu - Never seen previously!! A breakdown of QCD???

Peripheral AuAu - consistent with Ncoll scaling (large systematic error)€

RAA ( pT ) = d2N AA /dpT dηTAAd2σ NN /dpT dη


PHENIXPHENIXSemi-Semi-

Inclusive Inclusive 00 Au+Au Au+Au

ssNNNN=130 and =130 and 200 GeV200 GeV

vs pvs pTTPeripheral 60 -- 80%

Central 0-10%

S.S.Adler, et al, PRC 69, 034910 (2004)


Same data vs xSame data vs xTT on log-log plot on log-log plot


n(xn(xTT) point-by-point 200/130) point-by-point 200/130

• 0 xT scales in both peripheral and central Au+Au with same value of n=6.3 as in p-p

• (h+ + h-)/2 xT scales in peripheral same as p-p but difference between central and peripheral is significant


xxTT scaling of direct scaling of direct in p-p in p-p

PHENIX preliminary, K.Okada, H. Torii, et al, SPIN 2004, JPS2004


Recall Recall 00: n=5.1 works better for x: n=5.1 works better for xTT> 0.2> 0.2

n=6.3 n=5.1


xxTT scaling with Jets at the Tevatron scaling with Jets at the Tevatron a failure of QCD?a failure of QCD?

Ratio of Scaled Cross Sections 630/1800

• Exp’t n4= 0.448 n=4.45

• Theory n4= 0.559 n=4.56

• Either just outside or just touching the systematic errors?

J.Huston, Proc. ICHEP98, World Scientific also see CDF qcd www pages and G.C.Blazey & B.L.Flauger, ARNPS 49, 633 (99)


Backup Backup with PHENIX highlightswith PHENIX highlights


Central Spectrum is suppressed---is this Central Spectrum is suppressed---is this due to a shift caused by energy lossdue to a shift caused by energy loss

centralNcoll = 975 94TAA = 22.8 mb


RRAA AA : : High PHigh PTT Suppression to at least 10 GeV/c Suppression to at least 10 GeV/c

PRL 91 (2003) 072301

Binary scaling

Participant scaling

Factor 5

Large suppression in central AuAu - close to participant scaling at high PT

Peripheral AuAu - consistent with Ncoll scaling (large systematic error)€

RAA ( pT ) = d2N AA /dpT dηTAAd2σ NN /dpT dη


Cronin effect observed in d+Au at RHIC Cronin effect observed in d+Au at RHIC ssNNNN=200 GeV=200 GeV

PHENIX preliminary 0 d+Au vs centrality for DNP2003


Nuclear modification factor: Nuclear modification factor: ssNNNN dependence dependence for A+B collisionsfor A+B collisions

A.L.S.Angelis PLB 185, 213 (1987)WA98, EPJ C 23, 225 (2002)PHENIX, PRL 88 022301 (2002)D.d'E. PHENIX Preliminary QM2002

CERN: Pb+Pb (sNN ~ 17 GeV), (sNN ~31 GeV): all previous msmts B+A-Cronin enhancement

Ncollision scaling

Npart scalingRAA ~ 0.4 RAA~0.2

RAA ~ 2.0

RAA ~1.5

RHIC Au+Au sNN=130 and 200 GeV HUGE SUPPRESSION---Major Discovery 2001-2


Spectra are suppressed for more central collisions---Spectra are suppressed for more central collisions---is this due to a shift caused by energy loss?is this due to a shift caused by energy loss?

•RAA(pT)=constant for pT> 4• d/pTdpT is pT

-8.1

€

1− ΔE( pT )pT

⎛ ⎝ ⎜

⎞ ⎠ ⎟8.1−1

= RAA ( pT )

€

1− RAA (pT )1

8.1−1 = ΔE( pT )pT

= const

• pT for d/dpT


|k|kTyTy|| from pp and dAufrom pp and dAu

z =0.75 taken as constant

kT-broadening increases with pTtrig as as at lower s

no difference in dAu and pp!

need lots more data in both pp and p(d)+Au


|j|jTyTy|| and and zz |k|kTyTy|| in Au+Auin Au+Au

pp <z><|kTy|>

pp <|jTy|>

(2.5pTtrigg4.0)(1.0pTassoc2.5) (3.0pTtrigg5.0)(1.5pTassoc3.0)

There seems to be significant broadening of the away-side correlation peak which persists also at somewhat higher pT range.

PHENIX preliminary QM2004


UA2 results on cosUA2 results on cos* and k* and kTT in direct in direct

R. Ansari, et al, UA2, ZPC 41, 395 (1988)

m. j. tannenbaum brookhaven national laboratory upton, ny 11973 usa

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pp collisions

p p collisions

bjorken scaling

inclusive particle pt

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high pt production

ccrs fit pt

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