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RESERVE

RESERVE. Diffraction in optics. o) Forward peak for q =0 (diffraction peak) o) Diffraction pattern related to size of target and wavelength of beam. Diffraction in hadron scattering. p. p. p. p. p -. p 0. p. n. The spins and the masses squared of these particles are related:

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RESERVE

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  1. RESERVE

  2. Diffraction in optics o) Forward peak for q=0 (diffraction peak) o) Diffraction pattern related to size of target and wavelength of beam

  3. Diffraction in hadron scattering p p p p

  4. p- p0 p n The spins and the masses squared of these particles are related: J=a(t)=a(0)+a’ t This is the r trajectory, and is degenerate with thew, f2, a2 trajectories: the Reggeon J=a(t) t = M2 [GeV2] Digression on Regge theory Hadron-hadron interactions can be understood in terms of the exchange of trajectories. Egp-p--> p0n: In order to conserve all relevant quantum numbers, can only exchanger, r3, r5 (I=1, P=C=-1…)

  5. Digression on Regge theory The cross section for the interaction of hadrons a, b mediated by the exchange of a given trajectory is: For the total cross section to rise, ‘need’ a trajectory with intercept larger than unity: the Pomeron aP(t)=aP(0)+a’P t = 1.08 + 0.25 t

  6. Digression on Regge theory stot vs sqrt(s) pp pp Kp gp (Donnachie, Landshoff)

  7. VM p p Q2=0 MV=0.7 GeV ds/dt  exp(bt) b  10 GeV-2 VM: t-dependence Does the transverse size of the qqbar pair really shrink ? As in optical diffraction, the size of the diffractive cone is related to the size of the interacting objects -- t is the Fourier conjugate of the impact parameter b b (Rqq2 + Rp2) with Rp 5 GeV-2

  8. VM p p r0 b b Rp Rp MV2 For Q2 MV2  10 GeV2, qq pair has negligible size wrt proton small dipolepQCD Q2 VM: t-dependence • As in optical diffraction, size of diffractive cone related to • size of interacting objects – t is Fourier conjugate of impact parameter b • ds/dt  exp(bt)b (Rqq2 + Rp2) with Rp 5 GeV-2

  9. g* g p p e • Same final state as QED Bethe-Heitler •  interference •  access to real part of amplitude e e e p p p p Deeply Virtual Compton Scattering • Similar to elastic VM production, • but g instead of VM in final state • No VM wavefunction involved • Again rapid increase of cross section • with W

  10. g* g p p Deeply Virtual Compton Scattering In general, x1 x2: x2 x1 Generalised PDFs (also non-diagonal, skewed PDF): sensitive to parton-parton correlations in the proton ! Related to probability to find two partons with momenta x1, x2 Only accessible in diffraction ! NB diffractive reactions in general are sensitive to generalised PDFs: sensitivity largest for DVCS and heavy VM production. DVCS particularly clean since no wavefunction/hadronisation effects

  11. g* g p p s (gp gp) [nb] Generalised PDFs (GPDs) • Evidence of GPDs (so far) in DVCS and  production • In the kinematic regions • probed so far, GPDs are approximated by standard • PDFs, modulo a normalisation factor (2-3 in  case) • A field in its infancy. Holds the promise of mapping parton-parton correlations in the proton • Sensitivity to GPD modest at • HERA – largest at large x (JLab, Hermes, Compass…) GPD-based calculations

  12. Open Questions: • Detailed understanding of higher orders: • Dipole-model saturation vs saturation of parton densities at low x • Detailed understanding of helicity structure of diffraction: • sL vs sT, RD • GPDs – how do we extract H(x1,x2,t,Q2) from data ? vs Summary II • (Hard) diffraction calculable in QCD • Access to a novel quantity: GPDs, sensitive to 2-parton correlations in the proton • Saturation: a glimpse of the transition pQCD npQCD; connection to high-density QCD, colour glass condensate, RHIC

  13. Test factorisation in pp events (II) LRG LRG LRG vs • In addition to diffractive production of di-jets, measured diffractive • production of W, Z-bosons (CDF, D0); J/, b-mesons (CDF) • Rates are ~1% of the non-diffractive vs ~10% based on HERA PDFs • By comparing events with 1 LRG and those with 2 LRG: • Probability for 2 LRGs higher than (probability for 1 LRG)2, ie would • get different F2D from 1 LRG events than from 2 LRG events (CDF) • Fraction of diffractive dijets decreases with s (CDF, D0)

  14. Test factorisation in ppbar events (III) • More evidence of factorisation breaking in ppbar events: • Fraction of diffractive W production (CDF): • (1.15 ± 0.55)%vs 6% based on HERA PDFs • Fraction of diffractive b production (CDF): • (0.62 ± 0.19 ± 0.16)% vs  10% based on HERA PDFs • Fraction of diffractive J/psi production (CDF): • (1.45 ± 0.25)% vs  ??? % based on HERA PDFs • Fraction of diffractive dijets decreases with s and • increases for forward jets (D0) • ...

  15. F2D HERA predictions with rescattering DPE SD SD ND = 0.2 (exp: 0.19 ± 0.07) CDF data b Why is factorisation violated ? Violation of factorisation understood in terms of rescattering corrections of the spectator partons (Kaidalov, Khoze, Martin, Ryskin): • Two-component eikonal model a` la • Pumplin, Gribov. Assume: • Large-x valence is in predominantly • small configurations  rescattering • cross section small (colour transparency) • Small-x partons are in larger size configurations  rescattering cross section large

  16. Part III • A fashionable word: saturation • What does it mean ? • Relation with diffraction

  17. Saturation (Colour glass condensate) Qs2(x) 1/x Non perturbative region pQCD Q2 [GeV2] Transition pQCDnpQCD: saturation • When x  0 at Q2 > a few GeV2 • DGLAP predicts steep rise of • parton densities • At small enough x, this violates • unitarity [Gribov, Levin, Ryskin, 1983, • Mueller, Qiu, 1986, …] • Growth is tamed by gluon fusion • saturation of parton densities at • Q2=Qs2(x) • Gluon fusion  [xg(x,Q2)]2 F2D !! • Test transition to high-density QCD (cf RHIC, EIC, LHC…) • So far, no compelling evidence in the proton (seen in nuclei ??)

  18. r sqq Saturation g* r • Saturation occurs at “saturation scale” • Qs2(x)  [xg(x)]  1/xl • (proton denser at small x) • Models based on this picture • describe the data well (F2D, VM, DVCS, F2… -- RHIC data ??) • [Golec-Biernat,Wuesthoff,..] Saturation in p-rest frame • pQCD: sqq r21/Q2 • (colour transparency) • As Q2  0, sqq  • violation of unitarity • Growth tamed by sqq saturating • at sqq s(rp)

  19. Saturation vs data Inclusive DIS: Diffraction: xIPF2D(3) F2 Golec-Biernat,Wuesthoff, Bartels, Golec-Biernat, Kowalski Q2

  20. Saturation in the proton (II) Photon wave-function NB: sDiff more sensitive to saturation than stot: sDiff mainly probes intermediate dipole sizes, close to saturation region, r>Q/2, with r<Q/2 suppressed by extra power of Q2

  21. Dz~ 2RN (MN/PN) Saturation in nuclei • Consider a nucleus with large momentum • At small x, partons are poorly localised • longitudinally: Dz~1/(xPN) • Nucleus is squeezed because of boost. • Distance between two nucleons is • Dz~ 2RN (MN/PN) • For xN <1/(2RNMN) 0.1, partons from • different nucleons at same impact • parameter start to overlap • For xA<1/(2RAMN)=xA xN A-1/3, partons from all nucleons at same impact parameter overlap • high density fusion decrease of density

  22. xA xA xA Saturation in nuclei • F2A<F2N: smaller parton density in bound nucleon than in free nucleon: shadowing • shadowing: evidence of parton fusion/saturation ? • Perhaps… Q2 of data in shadowing region small • and correlated to x: • for x<10-2, Q2 < 1-2 GeV2 • perturbative ?! • EIC, eA at HERA…(s=??) F2A / F2N shadowing x

  23. The CMS experiment • Tracking • Silicon pixels • Silicon strips • Calorimeters • PbW04 crystals • for Electro-magn. • Scintillator/steel • for hadronic part • 4T solenoid • Instrumented iron • for muon detection • Coverage • Tracking • 0 < || < 3 • Calorimetry • 0 < || < 5 A Hugeenterprise ! Main program: EWSB, Beyond SM physics… A. De Roeck

  24. The TOTEM experiment TOTEM physics program: total pp cross section, elastic cross section Apparatus: Inelastic Detectors & Roman Pots (2 stations) CMS IP 150 m 215 m -t acceptance 10 m With special low * runs (* = 1000m) A. De Roeck

  25. TOTEM inelastic detectors TOTEM inelastic detectors Standard: T1/T2 Cathode Strip Chambers Not usable at medium/high lumi (>1033) Now: rethink T2 region (5<||<7-7.5) T2 T1 T2 T1 A. De Roeck

  26. Physics Program for CMS/TOTEM A. De Roeck • Soft & Hard diffraction • Gap survival dynamics, multi-gap events, proton light cone (pp3jets+p) • Diffractive structure: Production of jets, W, J/, b, t, hard photons • Diffractive Higgs production, (diffractive Radion production) • SUSY & other (low mass) exotics & exclusive processes • Low-x Dynamics • Parton saturation, BFKL dynamics, proton structure, multi-parton scattering… • Forward physics phenomena • New phenomena such as DCCs, incoherent pion emission,… • Strong interest from cosmic rays community • Forward energy and particle flows • Two-photon interactions and peripheral collisions • Forward physics in pA and AA collisions • Centauros and other Exotics • Use QED processes to determine the luminosity to 1% (ppppee, pppp) Many of these studies can be done best with L ~1033 (or lower)

  27. Status of the project • Common working group to study diffraction and forward physics at full LHC luminosity approved by CMS and TOTEM (ADR/ K. Eggert organizing) Use synergy for e.g. simulation, physics studies & forward detector option studies. Report back with EOI spring/summer 2004 • Detector options being explored • Roman Pot/microstations for beampipe detectors at 150, 215 , add 310 & 420 m ? Group starting (cold section!) • Inelastic detectors T1 and T2 CSC trackers of TOTEM Replace T2 with a compact silicon tracker (~ CMS technology) Add EM/HAD calorimeter (CASTOR) behind T2 Add Zero degree calorimeter (ZDC) at 140 m • Common DAQ/Trigger for CMS & TOTEM • Common simulation etc… A. De Roeck

  28. New T2 tracker A. De Roeck CMS TRACKER Silicon Strip detectors Single side p+ strips on n-type substrate, thickness=320 mm, AC-coupled, pitch 80~205 mm, Radiation hardness up to 1.6x1014 1MeV equ./cm2, Cold enviroment –20oC. CMS tracker T2 h range : 5.3 < h < 6.7 Distance from IP: 13570 mm T2 inner radius: 25 mm + 8 mm = 33mm  Vacuum chamber inner radius: 25 mm Outer radius: 135mm  Length: 400 mm Under study by TOTEM

  29. Forward Calorimeter A. De Roeck A calorimeter in the range 5.3 < e< 6.8 (CASTOR) Position of T2 and Castor (7/2/03) 13570 T2 CASTOR Tungsten and quartz fibres Length 152 cm~ 9I Electromagnetic section 8 sectors/ needs extension

  30. Alternative Detectors A. De Roeck -station concept (Helsinki proposal) Silicon pixel detectors in vacuum (shielded) Very compact Maybe for detectors at 400 m? Needs test-setup Movable detector

  31. Roman Pot Acceptances A. De Roeck MAD calculations acceptance 0.003(2) <<0.15 10s 20s

  32. A. De Roeck

  33. Khoze, Martin,Ryskin Orava, De Roeck hep-ph/0207042 Compare different processes for light Higgs discovery at the LHC 3 Numbers for 30 fb-1 and a Higgs of 120 GeV A light Higgs will be a challenge for the LHC!

  34. Diffractive Higgs production at LHC

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