1 DIFFRACTION and Forward Physics – 2 DIFFRACTION and Forward Physics – 2 M. Arneodo, M.Diehl, V.A.Khoze, P.Newman & with a bit of personal flavour Plan 1. New theoretical results presented at the 4 th Workshop 2. Selected hot topics: survival of the survival factor, basic soft cross-sections at the LHC 3. What can HERA still provide ? 4. Selected early LHC measurements to test predictions for diffractive processes Apologies to those excellent & enthusiastic speakers, whose results were not (properly) covered (lack of time or / and expertise) by popular demand

2 Theory Talks Theory Talks Selection: -as seen through the eyes of the needs of Forward Physics Community -minimal overlap with other WGs some overlap : SATURATION  JB – nontrivial task of transferring a theoretical description of saturation from HERA to the LHC  K. G-B, GW –sensitivity of the Diffractive DIS to the saturation  sat. effects quantified- GW (  -part)

3 Selection rules mean that central system is 0 ++  pinning down the quantum numbers CP violation in the Higgs sector shows up directly as azimuthal asymmetries Tagging the protons means excellent mass resolution (~ GeV) irrespective of the decay products of the central system. LO QCD backgrounds suppressed Proton tagging may be the discovery channel in certain regions of the MSSM. Unique access to a host of interesting QCD processes Very schematically: exclusive central production is a glue – glue collider where you know the beam energy of the gluons - source of pure gluon jets - and central production of any 0 ++ state which couples strongly to glue is a possibility … Exclusive Central Production Very promising addition to the ‘party line’ Higgs studies at the LHC and even at the ILC/CLIC (KMR, J.Ellis et al, Manchester group ) (~10 talks) (gg)CED  bb

4 (P. Bussey, C. Royon) H Improved during this Workshop, coming soon (already a bit outdated)

5 Process WWA spectrum p p CMS Near beam Detectors Photon-photon and photon-proton LHC Extensive Program   , ee QED processes   QCD (jets..)   WW anomalous couplings   squark, top… pairs   BSM Higgs   Charginos  … …and  p (P. Bussey, J. Nystrand,M. Strikman)

6 LHC as a High Energy  Collider KMR-02 p p

7 γγ PHOTOPRODUCTION Cross sections for various γγ processes. The dimuon process may be good for LHC luminosity monitoring. W + W - has a large cross section of 100 fb. (P. Bussey )

8 Recently -renewal of the interest KMR-02 BAD NEWS

9 Exclusive Channels in pp -collisions Exclusive Channels in pp -collisions G. Watt, L.Motyka, A.Martin, J.Nystrand (GW, LM, JN) exclusive J/  from HERA data as an independent source of information on unintegr. gluons, needed for the H-Central Excl. Higgs Production (TT,GW) Exclusive  production at the LHC as probe of unintegrated gluons (GW, AM) in a peaceful coexistence a nice way to search for the Odderon ( LM, AM, JN) a potential discovery channel Give us unintegrated gluons in advance (P.Bussey )

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11 (ALICE, LHCb) (L. Motyka, A.Martin)  exch odderon exch (R. Schicker, , J/  - RG)

12 G. Watt, L.Motyka (good agreement with J.Nystrand and KMR ) (“blessed”) (J. Pinfold)

13 Selected Hot Topics Selected Hot Topics Importance for the Forward Physics Studies at the LHC Serve as a litmus paper indicator of the level of our knowledge (theory & experiment) on diffractive physics at high energies Account for the absorption effects -necessitated by unitarity Survival of the Survival Factor (Regular talks by U. Maor (GLM), A. Martin (KMR) and M. Strikman (FHSW)) S² -a crucial ingredient of the calculations of the rate of the Central Excl. Diffractive processes +….. Prospects of New Physics studies in the Forward Proton mode qualitatively new stage – a ‘delivery’ of our meetings orders of magnitude differences in theoretical expectations – are a history (not so long ago- between Scylla and Charybdis) new (encouraging) CED Tevatron results available, more results to come ( K. Goulianos, J. Pinfold) we are discussing now the differences on the level of a factor of (4-5) ( M. Strikman ) conflict of interests

14 A killing blow to the wide range of theoretical models. arXiv: , PRD to appear soon (K. Goulianos)

15 PT LO undisputable

16 FHSW weak (~1/2) suppression (M. Strikman) (a factor of 4-5 diff. ) it might be much worse

17 Approach to the Black Disc Regime (how rapid is it above 2 TeV ?) 1. KMR  slow (logarithmic) rise by few % at the LHC 2. FHSW  BDR for energies  2 TeV (soft interactions and hard dipole-proton int. up to ) 3. GLM(M)  two components : ‘conservative’ + BDR-like START: at  2 TeV FINISH: BDR,=1

18  (tot),  (el),  ( SD ) Bread and butter of TOTEM and ALFA measurements I mportance for various LHC studies ( e.g. notorious Pile-Up) Low mass SD (DD)- one of the major current limitations on the models ( still not sufficient exp. Information) KMR-07, A. Martin: relatively low (about 20% below the ‘standard’ central value) value of  (tot ) at the LHC ( S.Sapeta and K. Golec-Biernat-05),  (tot)  90 mb …cosmic rays, (early) LHC tests – coming soon inescapable consequence of the absorptive corrections caused by the higher-mass excitations (A.Martin) GLM (arXiv; ):  (tot ) =110.5 mb,  (el) =25.3 mb (GLM)M (arXiv; ):  (tot ) = 92,1 mb,  (el) =20.9 mb KMR (A.Martin)  (tot ) = 90.5 mb,  (el) =20.8 mb GLM(M)- essential improvement of their description of the Tevatron elastic and SD data 

19 th

20 We have to be open-eyed when the soft physics is involved. Theoretical models contain various assumptions and parameters. Available data on soft diffraction at high energies are still fragmentary, especially concerning the (low mass) diffractive dissociation. Selection Criteria for the Models of Soft Diffraction A viable model should: incorporate the inelastic diffraction :SD, DD (for instance 2-3 channel eikonal of KMR or GLM(M)) describe all the existing experimental data on elastic scattering and SD,DD and CED at the Tevatron energies and below (A. Martin; GLM(M), ) be able to explain the existing CDF data on the HERA-Tevatron factorization breaking and on the CED production of the di-jets, di-photons, , J/ , .., lead. neutr. at HERA provide testable pre-dictions or at least post-dictions for the Tevatron and HERA So far KMR model has passed these tests. Only a large enough data set would impose the restriction order on the theoretical models and to create a full confidence in the determination of S². Program of Early LHC measurements (KMR, A. Martin) LET THE DATA TALK !

21 What can HERA still provide ? test higher twists t- depencences (VM, (V)FPS) Odderon searches (From DIS08)

22 More detailed data on proton dissociation in diffractive J/  production (better statistics, M ²- slicing ). Improved statistics on exclusive  - production (not sufficient at the moment). The ratio of diffractive to exclusive dijets, photo to electroproduction. Transverse momentum distribution of secondaries in the ‘Pomeron fragmentation’.

23 The Extraction of the Bare Triple-Pomeron Vertex -a crucial ingredient for understanding diffraction (e.g. S ² calc.)  Bare A way to extract the information on    KMR-06  Importance of an explicit measurement of the Y-system mass spectrum. To perform a full triple-Regge analysis with different contributions quantified. (by integration over ZEUS range) (dress code) (after acconting for the second. traject.)  0.2 (A. Martin) Existing (ZEUS) data on J/  -still fragmentary Needed: - improved statistics; -distributions over M²Y -inelast. diffractive  data; small size- component (small rescatter. effects)

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25 Are the early LHC runs, without proton taggers, able to check estimates for pp  p+A+p ? Possible checks of: (i) survival factor S 2 : W+gaps, Z+gaps (ii) generalised gluon f g :  p   p (iii) Sudakov factor T :  3 central jets (iv) soft-hard factorisation #(A+gap) evts (enhanced absorptive corr n ) #(inclusive A) evts with A = W, dijet,  … gap KMR: (A. Martin) Divide et Impera

26 y=-ln ,  =(1-x) High sensitivity to the parameters of models for Soft Diffraction LHC with 220m and 420m Forward Taggers TOTEM, ALFA, ALICE (RG) ?

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28 Backup

29 (M.Strikman)

30 S 2 ~ 0.02 Watt (A. Martin)

31 Exposing the contribution of the Perturbative Pomeron to DDIS (G. Watt, A.Martin and M. Ryskin (2006)) The perturbative.resolved Pomeron contribution. Measurements of the k t of secondaries in the ‘Pomeron fragmentation’ (edge of LRG). The kt distribution of the lowest jet should obey the power law – in marked contrast with the expectations based on Regge-factorization. Larger k t of the secondaries with the long power-like tail should be observed. Nonperturbative resolved Pomeron.

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34 P. Bussey H Very promising addition to the ‘party line’ Higgs studies at the LHC and even at the ILC/CLIC (KMR, J.Ellis et al, Manchester ) Improved during this Workshop, coming (very) soon