Presentation is loading. Please wait.

Presentation is loading. Please wait.

Max-Planck-Institut für Kernphysik, Heidelberg Two scales of the hadronic structure Search for clean signatures in the data Bogdan Povh.

Similar presentations


Presentation on theme: "Max-Planck-Institut für Kernphysik, Heidelberg Two scales of the hadronic structure Search for clean signatures in the data Bogdan Povh."— Presentation transcript:

1 Max-Planck-Institut für Kernphysik, Heidelberg Two scales of the hadronic structure Search for clean signatures in the data Bogdan Povh

2 Max-Planck-Institut für Kernphysik, Heidelberg Introduction Diffractive cross section is surprisingly small Hadronic cross sections rise slowly Diffractive cone hardly shrinks with energy Gluon shadowing is weak Conclusion "anschaulich" Gluonic mini-clouds of the valence quarks

3 Max-Planck-Institut für Kernphysik, Heidelberg Introduction The first evidences for the smallness of the gluonic clouds come from the ISR- experiments but they have been formally interpreted within the Regge-phenomenology with no connection to hadronic structure (small triple pomeron coupling)

4 Max-Planck-Institut für Kernphysik, Heidelberg Introduction I will reinterpret the data in a less formal way, showing that the weakness of diffraction is related to smallness of gluonic clouds. I will argue that the radius of the gluonic spots suggested by data is about 0.3 fm. This is small as compared to to the confinement radius of 1 fm (in fact one has to compare these numbers squared)

5 Max-Planck-Institut für Kernphysik, Heidelberg Introduction Theoretically small r 0 =0.3 fm is not a surprise. 1.Lattice-calculation 2.Instanton-liquid model 3.Quark model with gluons of m g =0.8 GeV

6 Max-Planck-Institut für Kernphysik, Heidelberg Introduction Any high energy reaction via the strong interaction carries the information on the size of the gluon cloud. But, in general, cannot be unambiguously interpreted. Diffraction seems to be the unique way to probe directly the gluonic structure of hadrons.

7 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction At high energies and large M x diffraction is dominated by gluon bremsstrahlung. MxMx Colorless exchange

8 Max-Planck-Institut für Kernphysik, Heidelberg At low energies the neutral object is qq exchange (Regge exchange) but the cross section drops with energy ~ s -1/2 and M x dependence Diffraction The gluon bremsstrahlung gives different M x dependence because the gluon is a vector particle

9 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction The 1/M 2 mass distribution at fixed s and t is the signature of gluon bremsstrahlung. Analogy to photon bremsstrahlung in spite of the difference of photon and gluon.

10 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction...

11 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction Inclusive cross section for the reaction pp->pX at ISR

12 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction scalinggluon bremsstrahlung g P pp (g P pp ) 2 ~ tot P: Pomeron ln (s/M x 2 ) = rapidity gap g P pp

13 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction The Pomeron- proton total cross section naïve expectation:

14 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction The gluon cloud of the valence quark is small. r 0 2 = 0.1 fm 2 Neither the single gluon comes far from the quark nor two gluons can couple to the color singlet if they are more than 0.3 fm apart.

15 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction in DIS Similar results are obtained in diffraction in DIS from the H1 and ZEUS data by Hauptmann und Soper. p p q x q r 0 = 0.2 fm

16 Max-Planck-Institut für Kernphysik, Heidelberg Proton-proton cross section Schematic total cross sections of pions, kaons, protons/antiprotons and photons on the proton

17 Max-Planck-Institut für Kernphysik, Heidelberg Proton-proton cross section Random walk The transverse distances between the quarks s independent The s dependence comes from the gluon bremsstrahlung R0R0 R

18 Max-Planck-Institut für Kernphysik, Heidelberg Proton-proton cross section Our model: Kopeliovich, Potashnikova, bp and Predazzi Our prediction:Experiment:

19 Max-Planck-Institut für Kernphysik, Heidelberg Proton-proton cross section Differential cross sections of elastic pp and pp scattering. Imaginary part of partial amplitude as a function of the impact parameter.

20 Max-Planck-Institut für Kernphysik, Heidelberg pp (solid circles) and pp (open circles) cross sections at s 1/2 > 10 GeV elastic slope and our predictions Proton-proton cross section

21 Max-Planck-Institut für Kernphysik, Heidelberg Photoproduction of J/ It is good to have a hadron-proton elasctic scattering far away from the unitary limit. and agree with our parameters before the unitary correction.

22 Max-Planck-Institut für Kernphysik, Heidelberg Photoproduction of J/ Differential cross sections for the exclusive photoproduction of J/

23 Max-Planck-Institut für Kernphysik, Heidelberg Photoproduction of J/ Values of the slope b, of the t distribution, plotted as a function of W.

24 Max-Planck-Institut für Kernphysik, Heidelberg

25

26 Gluon shadowing x Boost Reduction of the gluon density by x

27 Max-Planck-Institut für Kernphysik, Heidelberg Gluon shadowing PQCD gives huge shadowing. Observed small. For shadowing one needs also transverse overlap.

28 Max-Planck-Institut für Kernphysik, Heidelberg Conclusion "anschaulich" J Chew-Frautschi plot

29 Max-Planck-Institut für Kernphysik, Heidelberg Conclusion "anschaulich" Chew-Frautschi plot The Regge trajectory simulates the collective effect of exchanging all members of a family of particles. When t is negative it is the square of the momentum transferred in the exchange. Positive t is the squared mass of the physical particles of spin 1, 3, 5,...

30 Max-Planck-Institut für Kernphysik, Heidelberg Conclusion "anschaulich" For linear potential (string) gives m 2 ~ J slope naive expectation for ' P = 4/9 0.9 GeV -2 = 0.4 GeV -2 measured ' P = 0.1 GeV -2 P = 8 GeV/fm

32 Max-Planck-Institut für Kernphysik, Heidelberg

33 Color glass codensate = gluon shadowing as function of k One would expect: 1 0 k

34 Max-Planck-Institut für Kernphysik, Heidelberg Diffraction h1-x x kTkT -k T MxMx

35 Max-Planck-Institut für Kernphysik, Heidelberg Measurements of, b 0, and (0) obtained separately from the electron and muon decay channels. Photoproduction of J/


Download ppt "Max-Planck-Institut für Kernphysik, Heidelberg Two scales of the hadronic structure Search for clean signatures in the data Bogdan Povh."

Similar presentations


Ads by Google