slide1
Download
Skip this Video
Download Presentation
Proton

Loading in 2 Seconds...

play fullscreen
1 / 50

Proton - PowerPoint PPT Presentation


  • 153 Views
  • Uploaded on

Small-x and Diffraction in DIS at HERA II Henri Kowalski DESY 12 th CTEQ Summer School Madison - Wisconsin June 2004. Dipole Saturation Models. Proton. GBW. b – impact p. BGBK. DGLAP. IIM Model with BFKL & CG evolution. KT. Glauber Mueller. T(b) - proton shape.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Proton' - infinity


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Small-x and Diffraction in DIS atHERAIIHenri KowalskiDESY 12thCTEQ Summer School Madison - Wisconsin June 2004

slide2

Dipole Saturation Models

Proton

GBW

b – impact p.

BGBK

DGLAP

IIM Model with BFKL & CG evolution

KT

Glauber

Mueller

T(b) - proton shape

slide3

Derivation of the GM dipole cross section

probability that a dipole at b

does not suffer an inelastic

interaction passing through

one slice of a proton

Uncorrelated scatterings

S2 -probability that a dipole

does not suffer an inelastic

interaction passing through

the entire proton

  • NOTE: the assumption of
  • uncorrelated scatterings is
  • not valid for BK and JIMWLK
  • equations
  • Correlations from evolution
  • IIM Dipole fit

GM Dipole + DGLAP mimics

full evolution

<= Landau-Lifschitz

slide4

Data precision is essential to the progress of understanding

GBW

GBW

GBW

Parameters fitted to HERA DIS data: c2 /N ~ 1

s0 = 23 mb l = 0.29 x0 = 0.0003

slide5

lGBW=0.29

----- universal rate of rise of all

hadronic cross-sections

Smaller dipoles  steeper rise

Large spread of leff characteristic for

Impact Parameter Dipole Models (KT)

slide6

Analysis of data within Dipole Models

BGBK

lGBW=0.29

KT

GBW

In GBW Model change of l with Q2 is

due to saturation effects

In IP Saturation Model (KT) change

of l with Q2 is mainly due to

evolution effects

In BGBK Model change of l with Q2 is

due to saturation and evolution effects

Theory (RV): evolution leads to saturation - Balitzki- Kovchegov and

JIMWLK

slide7

GBW - - - - - - - - - - - - - - - - - - - - -

x = 10-6

BGBK ___________________________________

x = 10-2

Evolution increases gluon density =>

smaller dipoles scatter stronger,

gluons move to higher virtualities

Fourier

transform

x = 10-4

- numerical evaluation

x = 10-2

In Color-Glass gluons occupy higher

momentum states

slide8

A glimpse into nuclei

Naïve assumption for T(b):

Wood-Saxon like, homogeneous, distribution of nuclear matter

slide9

Smooth Gluon Cloud

Q2 (GeV2)

C 0.74 1.20 1.70

Ca 0.60 0.94 1.40

slide10

Lumpy Gluon Cloud

Q2 (GeV2)

C 0.74 1.20 1.70

Ca 0.60 0.94 1.40

slide12

_

Diffractive production of a qq pair

slide15

Non-DiffractionDiffraction

<=p

e =>

Select diffractive events by requirement of

no forward energy deposition

called hmaxcut

Q: what is the probability that a non-diff event

has no forward energy deposition?

slide16

MX Method

Non-Diffractive Event Diffractive Event

detector

detector

log W2

log MX2

DY

Y

Y

DY

g*

g*

p

p

g*p-CMS

g*p-CMS

non-diff events are characterized by

uniform, uncorrelated particle emission

along the whole rapidity axis =>

probability to see a gap DY is

~ exp(-lDY)

l – Gap Suppression Coefficient

diff events are characterized by

exponentially non-suppressed

rapidity gap DY

since DY ~ log(W2/M2X) – h0

dN/dlogM 2X ~exp( l log(M 2X))

dN/ dM 2X ~ 1/ M 2X =>

dN/dlogM2X ~ const

slide17

MX Method

diff

diff

diff

Non-

diff

Non-

diff

Non-

diff

Non-Diffraction

dN/dM 2X ~exp( l log(M 2X))

Gap suppression coefficient l

independent of Q2 and W2

for Q2 > 4 GeV2

Diffraction

dN/dlog M 2X ~ const

gap suppression in non diff mc
Gap Suppression in Non-Diff MC

---- Generator Level CDM

---- Detector Level CDM

Detector effects

cancel in

Gap Suppression !

dN/dM 2X ~exp( llog(M 2X))

In MC l independent of Q2 and W2

l~ 2 in MC

l~ 1.7 in data

physical meaning of the gap suppression coefficient l
Uncorrelated Particle Emission (Longitudinal Phase Space Model)

l – particle multiplicity per unit of rapidity

Feynman (~1970): l depends on the quantum numbers carried by the gap

l = 2 for the exchange of pion q.n. (a=0)

= 1 for the exchange of rho q.n. (a=1/2)

= 0 for the exchange of pomeron q.n. (a=1)

l- is well measurable provided good calorimeter coverage

Physical meaning of the Gap Suppression Coefficient l

exp(- lDY ) = exp(-llog(W2/M2X)= (W2/M2X)-l

from Regge point of view ~ (W2)-2(1-a)

slide29

Absorptive correction to F2

from AGK rules

  • Martin
  • M. Ryskin
  • G. Watt

Example in Dipole Model

F2 ~

-

Single inclusive

pure DGLAP

Diffraction

agk rules
AGK Rules

QCD

Pomeron

The cross-section for k-cut pomerons:

Abramovski, Gribov, KancheliSov. ,J., Nucl. Phys. 18, p308 (1974)

1-cut

F (m) – amplitude for the exchange of

m Pomerons

1-cut

2-cut

slide32

Pomeron in QCD

t-channel picture

Color singlet dominates over octet

in the 2-gluon exchange amplitude

at high energies

3-gluon exchange amplitude is suppressed

at high energies

2-gluon pairs in color singlet (Pomerons)

dominate the multi-gluon QCD amplitudes

at high energies

slide33

2-Pomeron exchange in QCD

Final States

(naïve picture)

detector

Diffraction

0-cut

DY

g*

p

g*p-CMS

<n>

1-cut

g*

p

g*p-CMS

detector

<2n>

2-cut

g*

p

g*p-CMS

slide34

0-cut

1-cut

2-cut

3-cut

agk rules in the dipole model
AGK Rules in the Dipole Model

Total cross section Mueller-Salam (NP B475, 293)

Dipole cross section

Amplitude for the exchange of m pomerons in the dipole model

KT model

slide36

AGK rules

Dipole model

Diffraction from AGK rules

very simple

but not quite

right

slide39

Q2~1/r2

exp(-mq r)

slide40

All quarks

Charmed quark

slide45

Conclusions

We are developinga very good understanding of inclusive and

diffractive g*p interactions:

F2 , F2D(3) , F2c , Vector Mesons (J/Psi)….

Observation of diffraction indicates multi-pomeron interaction

effects at HERA

HERA measurements suggests presence of Saturation phenomena

Saturation scale determined at HERA agrees with the RHIC one

Saturation effects in ep are considerably increased in nuclei

slide46

Thoughts after CTEQ School

George Sterman: Parton Model Picture (in Infinite Momentum Frame)

is in essence probabilistic, non-QM. It is summing probabilities and

not amplitudes

F2 = f e2f x q(x,Q2)

Parton Model Picture is extremely successful, it easily carries information

from process to process, e.g. we get jet cross-sections in pp from

parton densities detemined inep

Dipole Models (Proton rest Frame) are very successful carrying information

from process to process within ep. They are in essence QM, main objects

are amplitudes:

In DM Picture diffraction is a shadow of F2 . Many other multi-pomeron

effects should be present

slide47

Several attempts are underway to build a bridge over the gap

between

Infinite Momentum Frame and Proton Rest Frame Pictures

Jochen Bartels, Lipatov & Co:

Feynman diagrams for multi-pomeron processes…

Raju Venogopulan & Co,

Diffraction from Wilson loops, fluctuations from JIMWLK…

……………………………………..

a new detector to study strong interaction physics
A new detector to study strong interaction physics

p

Si tracking stations

EM Calorimeter

Hadronic

Calorimeter

Compact – fits in dipole magnet with inner radius of 80 cm.

Long - |z|5 m

e

slide49

Forward

Detector

e

27

GeV

p

920

GeV

slide50

HERA Interactions

Collisions of e+ (e-) of 27.5 GeV with p of 920 GeV

Increase of kinematic range by over 4 order of magnitude

in x at moderate Q2 and6 order of magnitude in Q2

ad