high energy physics seminar university of connecticut 7 february 2005 konstantin goulianos the...

High Energy Physics Seminar

University of Connecticut7 February 2005

Konstantin Goulianos

The Rockefeller University

QCD ASPECTS OF HADRONIC DIFFRACTION

CDF results Comparison with HERA QCD aspects Tev2LHC

UC seminar, 7 Feb 2005 QCD Aspects of HadronicDiffraction K. Goulianos 2

What is Dark Energy?

* * ** * *

H He

E

M

* * ** * *

H He

E

M


Rapidity Gaps

Gaps are exponentially suppressed

From Poisson statistics:

dy

dneyP y )(

(=particle density in rapidity space)

Rapidity gaps are formed bymultiplicity fluctuations.

Non-diffractive interactions

Bj, PRD 47 (1993) 101: regions of (pseudo)rapidity devoid of particles

ε122

0t M

1~

dM

dσΔy2εe~Δyd

dσ

2lnlnln Msy

Rapidity gaps at t=0 grow with y.Diffractive interactions

pp /

2: negative particle density!


Forty Years of Diffraction

1960’s BNL: first observation of pp -> pX

1970’s Fermilab fixed target, ISR, SPS Regge theory & factorization

Review: KG, Phys. Rep. 101 (1983) 169

1980’s UA8: diffractive dijets hard diffraction

1990’s Tev Run-I: Regge factorization breakdownTev/ HERA: QCD factorization breakdown

21st C Multigap diffraction: restoration of factorizationIdeal for diffractive studies @ LHC

http://physics.rockefeller.edu/dino/my.html


The First 20 Years The First 20 Years

KG, Phys. Rep. 101 (1983) 171

XLL/PΔPξ

1

~d

d

constantyd

dσ

M

1~

dM

dσ22

POMERON: color singlet w/vacuum quantum numbers

s

M

p

Δpξ

2

L

L y

y

2ln M

slnln

y025.0dMdt

σd2

2

t


The Last 20 Years

93(2004)141601


valence quarks

antiproton

x=

Diffraction in QCD

proton

)or(1

)( xxfx

g=0.20

q=0. 04

R=-0.5

g=0.5

q=0.3

SOFT HARD

deep sea

Derive diffractivefrom inclusive PDFsand color factors

antiproton

valence quarks

pp


CDF in Run I-0 (1988-89)Elastic, single diffractive, and total cross sections @ 546 and 1800 GeV

Roman Pot Spectrometers

Roman Pot Detectors Scintillation trigger counters Wire chamber Double-sided silicon strip detector

Results Total cross section tot ~ s Elastic cross section d/dt ~ exp[2’ lns] shrinking forward peak Single diffraction Breakdown of Regge factorization

Additional DetectorsTrackers up to || = 7


Regge Theory


Unitarity problem: With factorization and std pomeron flux SD exceeds T at

Renormalization: normalize the pomeron flux to unity

Renormalization )(Mσξ)(t,f

dtdξ

σd 2XpIPIP/p

SD2

KG, PLB 358 (1995) 379

TeV.2s

1dtdξξ)(t,f0.1

ξ

IP/p

0

tmin

~10

2~ sSD


A Scaling Law in Diffraction

KG&JM, PRD 59 (1999) 114017

Factorization breaksdown in favor of

M2-scaling

12

2

2 )(M

s

dM

d

renormalization

1


The QCD Connection

ytel etsf ),(Im

y sy ln

The exponential rise of T(y’) is dueto the increase of wee partons with y’

(see E. Levin, An Introduction to Pomerons,Preprint DESY 98-120)

yooT ess )(

y sy ln

Total cross section:power law rise with energy

Elastic cross sectionforward scattering amplitude

s


yy

yt ,2 independent variables:

yo

ytp eetFC

yddt

d

222

)(

Gap probability

Renormalization removes the s-dependence SCALING

QCD Basis of Renormalization

ye 2~ 22ln

minsyssy

y

t

colorfactor

17.0)0(

)(

ppIP

IPIPIP tg

(KG, hep-ph/0205141)


The Factors and

Experimentally: KG&JM, PRD 59 (114017) 1999

g=0.20

q=0.04

R=-0.5

fg=gluon fractionfq=quark fraction

λx

1f(x)x

18.03

125.0

8

175.0

121f

1

1f

2

Q

NN cq

cgColor factor:

12.0ww qqgg Pomeron intercept:

104.0,02.017.0

pIP

IPIPIPg

λ

/sxs~dxxf

1

1)(

CTEQ5L


Run-I A,B: Rapidity Gap Studies

Forward DetectorsBBC 3.2<<5.9FCAL 2.4<<4.2


Double Diffraction Dissociation

One central gap

Double Pomeron Exchange

Two forward gaps

SDD: Single+Double Diffraction One forward + one central gap

Central and Double Gaps


2122

2-1i1

2

51

5

)( yyo

ytp

ii

eetFCdV

dii

Gap probability Sub-energy cross section(for regions with particles)

Multigap Renormalization

ye 2~ 22ln

minsyssy

y

Same suppressionas for single gap!

1y 2y1y 2y

1y 2y

1t 21 yyy 5 independent variables

2t colorfactors

(KG, hep-ph/0205141)


One-gap cross sections are suppressed Two-gap/one-gap ratios are 17.0

Central & Double-Gap ResultsDifferential shapes agree with Regge predictions

DD SDD DPE


Gap Survival Probability

0.23GeV)(1800S gapgap/01gapgap/12

0.29GeV)(630S gapgap/01gapgap/12

S =

Results similar to predictions by:Gotsman-Levin-MaorKaidalov-Khoze-Martin-RyskinSoft color interactions


Soft Diffraction Summary

M2 – scaling

Non-suppressed double-gap to single-gap

ratios

Experiment:

Phenomenology:

Generalized renormalization

Obtain Pomeron intercept and tripe-Pomeron coupling from inclusive PDF’s and color factors


SOFT DIFFRACTION

Hard Diffraction @ CDF HARD DIFFRACTION

Additional variables: (x, Q2)

seExjet

T

jetBj /

22 )(, jetTEQx

dN/d

=PL/PL =fractional momentum loss of scattered (anti)proton

Variables: (, t) or (,

t)

MX

=-lnt

dN/d

ln MX2


All fractions ~ 1% Factorization ~ OK @ Tevatron

at fixed c.m.s. energy.

Diffractive Fractions @ CDF

gap Xpp

1.45 (0.25)J/

0.62 (0.25)b

0.75 (0.10)JJ

1.15 (0.55)W

Fraction(%)X

SD/ND fraction at 1800 GeV


Diffractive DIS @ HERA

),(1

),,( 221

2)3(2 QQ xFxF D

eQ2*

p

jet

reorganize

J. Collins: Factorization should hold

e*

tp

IP

Pomeron exchange Color reorganization


Inclusive vs Diffractive DIS

CCF

Q

QQD

1212)3(

2

1

)()(

)(1),,(

2

P(0)-1(q)/2

F2 ~ x

q

KG, “Diffraction: a New Approach,” J.Phys.G26:716-720,2000 e-Print Archive: hep-ph/0001092


diff/incl DIS at HERA

At fixed x:flat Q2-dependence

At fixed Q2:flat x-dependence


Diffractive Dijets @ Tevatron

),/(1

),,( 22

21 QQ xFxF D

pjet

reorganizep

jet


CDF-ICRun-IC Run-IA,B

Forward DetectorsBBC 3.2<<5.9FCAL 2.4<<4.2


Roman Pot tracking


Diffractive Structure F‘n @CDF XJetJetppp

SD/ND Rates vs • Measure ratio of SD/ND dijet rates as a f’n of

• In LO-QCD ratio of rates equals ratio of structure

fn’s

px

45.0p0p

ND

SD xR)(xR

px

s

eE/ppx

2(3)

1i

iηiT

pqg,p

))(xq)(x(q

C

C)g(xx)(xF pipi

A

Fpppjj


FDJJ(,Q2) @ Tevatron

C

sx

CF

Q

QQD

2122111

)/(

)(1),,(

)(

22

2

εε

2sβ

1~

β

xξ1

ξ 211

renorm sβξ

dξN

minmin

min

)2(

)(1

121

~R2

RENORM

x

QsxSD

ND

4.02.0 xg


Tevatron vs HERA:Factorization Breakdown

dN/dgap dN/dgap

p

ppIP

CDF

H1

p

ppIP

e*

tp

IP

Predicted in KG, PLB 358 (1995) 379


Restoring Factorization

R(SD/ND)

R(DPE/SD)DSF from two/one gap:factorization restored!


CDF-II Tag leading p-bar @ 0.02 < < 0.1

Reject (retain) 95% of ND (SD)events

detectforwardparticle

s


MiniPlug Calorimeter

About 1500 wavelength shifting fibers of 1 mm dia. are ‘strung’ through holesdrilled in 36x¼” lead plates sandwiched between reflective Al sheets and guided

into bunches to be viewed individually by multi-channel photomultipliers.


Artist’s View of MiniPlug

25 in 5.5 in

84 towers


Diffractive dijets

=alltowers)ET e

s

momentum loss fraction of pbar

Approx. flat at <0.1

const

overlap events

SD region

MP energy scale: ±25% →Δlogξ = ±0.1RP acceptance (0.03<ξ< 0.1) ~ 80% (Run I)


: RP vs calorimeter

overlap events

signal region

cal distribution for slice of RP

from RP

cal = (0.94 ± 0.03)

RP

/mean ~ 30%


Q2-dependence of SD/ND ratio

No appreciable Q2 dependence

within 100 < Q2 < 10,000 GeV2

Pomeron evolves similarly to proton


Exclusive Dijets in DPEInterest in diffractive Higgs production Calibrate on exclusive dijets

Dijet mass fraction

X

conejj

jj M

MR

no peak!pb10534GeV25

pb27265970GeV10

0.8)(RσE jjjjexcl

DPEjetT

Upper limit for excl DPE-jjconsistent with theory: KMR 60 pb @ 25<ET

J<35 GeV


Gap Between Jets

jet???gap ΔyΔy Question

gapΔyjetΔy

5%1%/0.2/SR)s(R JGJTEV

JGJLHC

JetGapJetpp


CDF2LHC

TOPIC STATUS

(Q2, t) dependence of DSF close to ready

Exclusive c production close to ready

Low mass states in DPE need good trigger

Exclusive b-bbar production in DPE need b-trigger

-dependence of DSF need low lum run

Jet-gap-Jet w/jets in miniplugs need low lum run

compositeΔyΔy

BFKLΔyΔyjetgap

jetgap

gapΔyjetΔy


Summary

M2 – scaling

Non-suppressed double-gap to single-gap ratios

Flavor-independent SD/ND ratio

Little or no Q2-dependence in SD/ND ratio

SOFT DIFFRACTION

Universality of gap prob. across soft and hard diffraction Pomeron evolves similarly to proton

HARD DIFFRACTION

Diffraction appears to be a low-x partonic exchange subject to color constraints

high energy physics seminar university of connecticut 7 february 2005 konstantin goulianos the...

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