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d v. more flexible parametrization for extra W,Z Tevatron data. g. Run II Tevatron jet data require softer gluon ZEUS fit has no fixed target data. White,Thorne. Watt, Kowalski. Diffractive deep inelastic scattering (DDIS).

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  1. dv more flexible parametrization for extra W,Z Tevatron data

  2. g Run II Tevatron jet data require softer gluon ZEUS fit has no fixed target data

  3. White,Thorne Watt, Kowalski

  4. Diffractive deep inelastic scattering (DDIS)

  5. Conventionally DDIS analyses use two levels of factorisation - collinear factorization and Regge factorization collinear factn proved for DDIS (Collins), but important modifications in the HERA regime Regge factn

  6. Hint of problem with Regge factorisation assumption assumes Pomeron ~ hadron of size R Regge factn occurs in non-pert region m<m0, where m~1/R but aP(0)~1.2 from DDIS > aP(0)~1.08 from soft data  small-size component from pQCD domain with larger aP(0) New DDIS analysis---Watt, Martin, Ryskin Replaces Regge factorization by pQCD Collinear factorization, which holds asymptotically, must be modified in the HERA regime: -- inhomogeneous term in DGLAP evolution -- direct charm contribution -- twist-4 FLD component

  7. pert. contrib. rapidity gap

  8. given by pQCD inclusion of the inhomogeneous term makes gP smaller

  9. m2 fP  flux does not behave as 1/m2 convergence decreases as xP decreases

  10. but one of the HERA surprises…. global partons at g: valence-like S: Pomeron-like whereas expect lg ~ lS ~ 0.1 (xg ~ x –lg xS ~ x –lS ) Would have anticipated both driven by same vac. singularity

  11. need to introduce Pomeron made of col. singlet qq pair Pomeron made of two gluons as well as Now Pomeron flux factors depend on Sp as well as gp

  12. direct+resolved Pomeron (cf. photon) diffractive partons gD, qD can be used to predict diffractive processes with hard scale? Yes, but…

  13. soft rescatt. CDF diffr. dijet data gap gap CDF HERA

  14. Comments on GLM(2008) GLM include some 3P effects, but get <Senh2> = 0.063 <Stot2> = 0.0235 x 0.063 = 0.0015 Calculation should be extended to obtain reliable Senh • Need to calc. b, kt dep., Senh comes mainly from periphery • (after Seik suppression) where parton density is small. • So Senh (GLM) is much too small. • 2. First 3P diagram is missing, so sSD much too small. • 3. Four or more multi-Pomeron vertices neglected, so stot • asymptotically decreases (but GLM have stot asym. const.). • Model should specify energy interval where it is valid. • 4. Need to consider threshold suppression. • 5. Should compare predictions with observed CDF data.

  15. Comments on Strikman et al. also predict a v.small Senh ! They use LO gluon with steep 1/x behaviour. Obtain black disc regime at LHC energy, with low x gluon so large that only on the periphery of the proton will gap have chance to survive. However, empricially the low x, low Q2 gluon is flat – the steep 1/x LO behaviour is an artefact of the neglect of large NLO corrections. Again should compare to CDF exclusive data.

  16. “Enhanced” absorptive effects (break soft-hard factorization) rescattering on an intermediate parton: can LHC probe this effect ?

  17. inclusive diffractive A = W or dijet or U …. known from HERA

  18. A = W or U …. A = dijet pp  AX pp  AX+p rough estimates of enhanced absorption S2en

  19. MNRST – generalized PDFs at small x – arXiv 0812.3558 e.g. DVCS: skewing originates from uppermost cell, due the strong ordering in x in small x limit. So generalised parton distributions can be computed directly from known “global” diagonal PDFs Evolution: (x unchanged) anom.dim. of GN = anom.dim. of MN GPDF(x,x) diag. PDF(x) with Shuvaev transf. then gives GPDFs from moments with accuracy O(x) at small x at NLO. Typical diffractive processes have x~10-2 (ppp+H+p); x~10-3 (gpJ/y p)

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