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Forward PAG

Forward PAG. One of the 10 PAGs of CMS We are a genuine cross-borders PAG: Physics subjects range from QCD and EWK to Higgs and Exotica We are a across-political-boundaries PAG: (Attempt at) collaboration with TOTEM experiment FP420 R&D joint R&D project of ATLAS, CMS, LHC

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Forward PAG

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  1. Forward PAG One of the 10 PAGs of CMS We are a genuine cross-borders PAG: Physics subjects range from QCD and EWK to Higgs and Exotica We are a across-political-boundaries PAG: (Attempt at) collaboration with TOTEM experiment FP420 R&D joint R&D project of ATLAS, CMS, LHC In CMS, becoming a PAG has brought us into the mainstream: We have already two PAS to our name: “Exclusive dilepton and Upsilon photoproduction” PAS DIF-07-001 “Single diffractive W production” PAS DIF-07-002 We contribute to the iCSA08 exercise (Dimuon spectrum) We have a (unfortunately not very up-to-date) TWIKI page: https://twiki.cern.ch/twiki/bin/view/CMS/DiffractionAndFwdPhysics We have a hypernews forum https://hypernews.cern.ch/HyperNews/CMS/get/diffraction.html We meet every other week on Friday afternoon And we btw get more requests for conference talks than we can possibly fill Monika Grothe, UW meeting May 29 2008

  2. Forward physics Experimental definition: All processes for which particles produced At small angles and hence large Pseudorapidities provide a defining feature • = 90o   = 0 •  = 10o    2.4 • = 170o    -2.4 • = 1o    5.0 edge of coverage of central CMS/ATLAS detectors Monika Grothe, UW meeting May 29 2008

  3. Forward detectors CMS Hadronic Forward (HF) Hadronic Forward (HF) (3.0 < || < 5.0) (3.0 < || < 5.0) CASTOR CASTOR ZDC ZDC TOTEM T2 TOTEM T2 (|| > 8.1) (|| > 8.1) (5.2 < || < 6.6) (5.2 < || < 6.6) Not present in start-up TOTEM T1 TOTEM T1 TOTEM: Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Monika Grothe, UW meeting May 29 2008

  4. Forward detectors around CMS IP CMS has unprecedented calorimetric coverage, down to 6.5 for charged Particles and even more for neutral ones ATLAS cannot do this ! With FP420/Totem, CMS would also have unprecedented coverage for Detecting leading protons with momentum loss xi between 20% and 0.2% At nominal LHC optics,*=0.5m diffr peak TOTEM Points are ZEUS data FP420 xL=P’/Pbeam= 1-x Monika Grothe, UW meeting May 29 2008

  5. Physics with forward calorimetersand tracking detectors Proton PDF at very low x, parton evolution, saturation Particle and energy flow measurements Monika Grothe, UW meeting May 29 2008

  6. Low-x QCD - Saturation Saturation (Colour glass condensate) Qs2(x) 1/x Non perturbative region pQCD Q2 [GeV2] Structure function F2 P momentum fraction carried by parton • Steep rise in the gluon density at small x observed at HERA • Growth cannot continue indefinitely, would eventually violate unitarity • Growth tamed by gluon fusion: saturation of parton densities • So far not observed in pp interactions Monika Grothe, UW meeting May 29 2008

  7. Proton-proton collisions at low x Parton evolution The proton is a dynamic object ! Exact nature of dynamics not fully Understood: DGLAP, BFKL, saturation p CMS • Partons from each proton “decelerate” and meet to produce the hard scattering subsystem (ME) • Low x↔ long parton showers rapidity CASTOR → at LHC (for Q≳ 10 GeV and η = 6): xBjorken≳ 10-6→ xBjorken decreases by factor ~ 10 for each 2 units in rapidity p Monika Grothe, UW meeting May 29 2008

  8. PYTHIA DY • PYTHIA DY, η3 or η4∈ CASTOR • PYTHIA DY, η3 and η4∈ CASTOR qq → γ* → e+e− CASTOR acceptance window Proton pdf at low-x from Drell-Yan Forward lepton pairs EHKQS: “saturated” pdf with nonlinear terms in gluon evolution Kinematic coverage of CMS Castor calorimeter reaches down to <10-6 x1 >> x2 5.2 < ηe+,ηe− < 6.6 CTEQ5L → Cross section reduced by factor 2! EHKQS First time observation of saturation in pp possible ! Monika Grothe, UW meeting May 29 2008

  9. PYTHIA jets (MSEL=1)central dijet with pT > 60 GeV, |η| < 3 BFKL: large yield of high E forward jets ARIADNE (CDM) PYTHIA (DGLAP) jets “Jet energy” in CASTOR Forward jets from QCD evolution • x2≃x1 → X can be (di-)jets in central • CMS detector • In BFKL-like QCD-evolution forward jets can have large pT • Also possible: jet-gap-jet events Mueller-Navelet jets Sensitivity to BFKL dynamics Monika Grothe, UW meeting May 29 2008

  10. Measuring fwd particle and energy flow: Validation of hadronic shower models in cosmic ray physics → Models for showers caused by primary cosmic rays (PeV = 1015 eV range) differ substantially → Fixed target collision in air with 100 PeV center-of-mass E corresponds to pp interaction at LHC → Hence can tune shower models by comparing to measurements with T1/T2, CASTOR, ZDC Monika Grothe, UW meeting May 29 2008

  11. Physics with !(forward detectors) Hard diffraction Photon-photon physics Monika Grothe, UW meeting May 29 2008

  12. Forward physics:Escaping protons Elastic scattering Monika Grothe, UW meeting May 29 2008

  13. Diffraction in optics – Diffraction in hadron scattering p p p p o) Forward peak for q=0 (diffraction peak) o) Diffraction pattern related to size of target and wavelength of beam Monika Grothe, UW meeting May 29 2008

  14. Forward physics:Escaping protons Hard diffraction Monika Grothe, UW meeting May 29 2008

  15. Mind the gap: Gaps in the hadronic final state Selecting diffractive event Generated particles – energy weighted No color flow between proton and X Traditionally called “Pomeron exchange” X Diffractive sample generated with gap in –plus side dPDF Monika Grothe, UW meeting May 29 2008

  16. S2 … dPDF Diffraction with a hard scale: W prod • pp → p W X, W →sensitive to quark component of dPDFs • Rap gap based selection, i.e. no pile-up • Require absence of activity in the forward calorimeters (HF 3< || < 5, Castor 5.2 < || < 6.6 ) of CMS • For rap gap survival factor of S2 = 5%, arrive at O(100) evts/100pb-1 in the [n(Castor), n (HF)] = [0,0] bin • S/B  20 with Castor veto • Signal enhancement by ~30% due to diffractive dissociation 100pb-1 Other hard diffraction processes possible: Dijets, heavy quarks PAS DIF-07-002 Monika Grothe, UW meeting May 29 2008

  17.  physics: Exclusive dilepton production Monika Grothe, UW meeting May 29 2008

  18.  physics: Exclusive dilepton production Monika Grothe, UW meeting May 29 2008

  19.  physics: Exclusive dilepton production Monika Grothe, UW meeting May 29 2008

  20.  physics: Exclusive dilepton production • Nearly pure QED process • Absolute luminosity determination with precision of 4% is feasible • Selection via exclusivity condition in central detector + veto on CASTOR & ZDC activity • Calibration/alignment of proton taggers • rejection of 2/3 of p dissociative background with CMS fwd calorimeters pp → pp l+l− PAS DIF-07-001 ~700  events in 100 pb-1 with dominant background from p dissociative events (~200) ATLAS cannot do this ! Monika Grothe, UW meeting May 29 2008

  21. Vectormeson photoproduction ATLAS cannot do this ! pp→ ppϒ, ϒ→  PAS DIF-07-001 Possibility to measure pT2 slope: Monika Grothe, UW meeting May 29 2008

  22. Physics with near-beam proton taggers Monika Grothe, UW meeting May 29 2008

  23. shields color charge of other two gluons Vacuum quantum numbers “Double Pomeron exchange” Suppose you want to detect a light SM Higgs (say MH=120 GeV) at the LHC... Central exclusive production pp  pXp Suppression of gg  jet jet because of selection rules forcing central system to be (to good approx) JPC = 0++ SM Higgs with ~120 GeV: gg  H, H  b bbar highest BR But signal swamped by gg  jet jet Best bet with CMS: H  , where in 30 fb-1 S/√B  4.4 Monika Grothe, UW meeting May 29 2008

  24. dipole beam dipole p’ detector p’ detector Central exclusive Higgs production & FP420 shields color charge of other two gluons pp pHp with H (120GeV) -> bb • In non-diffractive production hopeless, signal swamped with QCD dijet background • Selection rule in CEP (central system is JPC = 0++ to good approx) improves S/B for SM Higgs dramatically • In particular beneficial for SUSY Higgs: Production cross section considerably higher than for SM May allow discovery of heavy SUSY Higgs bosons in LHC wedge region • CP quantum numbers & CP violation in Higgs sector • directly measurable from azimuthal asymmetry of protons Vacuum quantum numbers “Double Pomeron exchange” FP420 is an R&D project that proved the feasibility of putting proton detectors at 420m from the IP Decision whether FP420 will be built in CMS expected by this summer Proton spectrometer using the LHC beam magnets: Detect diffractively scattered protons inside of beam pipe Monika Grothe, UW meeting May 29 2008

  25. Beampipes Proton taggers @ 220m and 420m from IP TOTEM uses Roman pot technique to approach the beam with their Si detectors FP420, because of location in cryogenic region of LHC, uses movable beampipe Extremly rad hard novel Si technology: 3-d Silicon Cherenkov timing detectors with t ~ 10 ps to filter out events with protons from pile-up Monika Grothe, UW meeting May 29 2008

  26. H b, W, τ b, W, τ Discovery potential of CEP of Higgs CEP may be the discovery channel for MSSM Higgs: Heavy Higgs states decouple from gauge bosons, hence preferred search channels at LHC not available But large enhancement of couplings to bb,  at high tan Detailed mapping of discovery potential for pp→p + H,h + p CEP Higgs may also open door to discovery of an NMSSM Higgsin channel h  aa  4 which would be unique at the LHC Monika Grothe, UW meeting May 29 2008

  27. Summa Summarum Monika Grothe, Woekshop on high energy photon processes, CERN, April 2008

  28. Topics in the fwd PAG cover QCD – EWK – Higgs – Exotica Technically, our analyses replicate in part what other groups do (e.g. W selection from EWK, jets from QCD, etc) We look at corners of the phase space that the mainstream usually doesn’t look at: for example low pT end of the DY spectrum, quiet detector, etc Most of our topics are prime start-up topics For example J. Hollar is now leading the iCSA08 dimuon analysis In the next years the only area in CMS where additional detector construction may happen (FP420) Finally, already before FP420 upgrade, CMS has a fwd physics program that ATLAS cannot match Monika Grothe, Woekshop on high energy photon processes, CERN, April 2008

  29. Extra Monika Grothe, UW meeting May 29 2008

  30. Cross sections and production rates Rates for L = 1034 cm-2 s-1: (LHC) • Inelastic pp reactions: 109 / s • bb pairs 5 106 / s • tt pairs 8 / s • W  e n 150 / s • Z  e e 15 / s • Higgs (150 GeV) 0.2 / s • Gluino, Squarks (1 TeV) 0.03 / s • Diffraction 2.5 108 / s • Elastic scattering 2.2 108 / s • ~50% of the total cross section ! Monika Grothe, UW meeting May 29 2008

  31. A new way to probe the proton Single diffraction (SD): p p X X Double Pomeron exchange (DPE): Near-beam detectors central CMS apparatus IP IP central CMS apparatus rap gap IP Near-beam detectors Near-beam detectors In diffractive events look at the proton constituents through a lens that filters out all parton combinations except those with the vacuum quantum numbers If X = anything: Measure fundamental quantities of soft QC If X includes jets, W’s, Z’s, Higgs (!): Hard processes, calculable in perturbative QCD. Measure proton structure, QCD at high parton densities, discovery physics IP p p 2-gluon exchange: LO realisation of vacuum quantum numbers in QCD Monika Grothe, UW meeting May 29 2008

  32. Forward physics atnominal LHC optics The CMS+TOTEM (+FP420) joint program: Carry out a program of diffractive and forward physics as integral part of the routine data taking at CMS, i.e. at nominal beam optics and up to the highest available luminosities. This program spans the full lifetime of the LHC. CERN/LHC 2006-039/G-124 Monika Grothe, UW meeting May 29 2008

  33. Photon-mediated processes:Exclusive μμ production (di-muons) - (true) known rms ~ 10-4 • Calibration process both for luminosity and energy scales of near-beam detectors •  Striking signature: acoplanarity angle between leptons • Allows reco of proton  values with resolution of 10-4, i.e. smaller than beam dispersion •  Expect ~300 events/100 pb-1 after CMS muon trigger Monika Grothe, UW meeting May 29 2008

  34. Low-x QCD: Forward Drell-Yan Sensitivity to saturation: saturated PDF • Gives access to low-xBJ quarks in proton • in case of large imbalance of fractional • momenta x1,2 of leptons, which are then • boosted to large rapidities • CASTOR with 5.3 ≤ || ≤ 6.6 gives access to xBJ~10-7 • Measure angle of electrons with T2 • Pdf’s known at large xBJ, hence can extract pdf’s at low xBJ DY pairs suppressed in saturated PDF Monika Grothe, UW meeting May 29 2008

  35. Summary and Outlook (II) Still an opportunity for an original contribution to the LHC detectors ! possible addition possible upgrade RP220 with Si detectors SLHC Monika Grothe, UW meeting May 29 2008

  36. Side remark:Rapidity gap survival probability hard scattering jet dPDF • Diffractive PDFs: • probability to find a parton of given x under • condition that proton stays intact – • sensitive to low-x partons in proton IP dPDF b jet Closely related to the underlying event at the LHC • Proton and anti-proton are large objects, unlike pointlike virtual photon • In addition to hard diffractive scattering, there may be soft interactions among spectator partons. •  Fill rapidity gap & slow down outgoing protons  Hence reduce the rate of diffractive events. • Quantified by rapidity gap survival probability. F2D without and with rescattering effects CDF data b Predictions based on HERA diffractive PDFs Monika Grothe, UW meeting May 29 2008

  37. Inclusive SM Higgs production with H->WW* Two most important production channels Higgs boson likes mass Decays preferably into the heaviest particle kinematically possible Discovery potential already with ~1fb-1 for M(H) ~ 2M(W) Vector-Boson Fusion VBF channel could profit from CASTOR calorimeter Monika Grothe, UW meeting May 29 2008

  38. May profit from CASTOR which extends detector coverage to angles smaller than 1o Higgs Decay Tag jets f 1o 10o 90o 170o 179o  (non-linear scale) VBF SM Higgs production with H->WW* Contributes significant discovery potential In addition, may provide evidence for spin-0 Higgs, leptons prefer small  Monika Grothe, UW meeting May 29 2008

  39. Benefits from Castor calorimeter for Higgs Extends CMS calorimetric coverage in the very fwd direction, to below 1o wrt beam axis • Benefits for Higgs searches: • Provides handle on effect • of underlying events/multiple • parton-parton interactions • Use in Vector Boson Fusion • channels for detecting • forward tag jets W Monika Grothe, UW meeting May 29 2008

  40. CMS + TOTEM (+ FP420) CMS IP T1/T2, Castor ZDC RPs@150m RPs@220m possibly detectors@420m • TOTEM: • An approved experiment at LHC for measuringtot& elastic, at same IP as CMS • TOTEM aims at start-up on the same timescale as CMS • Expression of wish of CMS + TOTEM to carry out a joint physics program, with joint CMS+TOTEM data taking given to LHCC: “Prospects for diffraction and forward physics at the LHC” CERN LHCC 2006-039 G124, CMS note 2007-02, TOTEM note 06-5 • Possible addition FP420: • Proposal to install high precision silicon tracking and fast timing detectors close to the beams at 420m from the CMS IP • Proposal currently under scrutiny in CMS • If approved, could be installed in 2010 after LHC start-up Monika Grothe, UW meeting May 29 2008

  41. Forward instrumentation around CMS IP CMS central detector Hadronic Forward (HF) CASTOR IP 5 T1 T2 Zero Degree Calorimeter (ZDC) RP 147 RP 220 FP 420 IP 5 TOTEM: green CMS: blue Monika Grothe, UW meeting May 29 2008

  42. The CMS CASTOR calorimeter • extends the coverage to 5.2 < η < 6.6 • → enhances the hermiticity of CMS! • 14.37 m from the interaction point • octogonal cylinder with inner radius 3.7cm, outer radius 14cm and total depth 10.5 λI • signal collection through Čerenkov photons transmitted to PMTs through aircore lightguides • W absorber & quartz plates sandwich, with 45° inclination with respect to the beam axis • electromagnetic and hadronic sections • 16 seg. in φ, 14 seg in zno segmentation in η Currently funding available only for CASTOR on one side of IP If LHC allows, installation of 1/2 CASTOR on one side of IP 07/2008 Monika Grothe, UW meeting May 29 2008

  43. The CMS Zero Degree Calorimeter • 140 m from interaction point in TAN absorber • Thungsten/quartz Čerenkov calorimeter with separate e.m. (19 X0) and had.(5.6 λI) sections • em: 5-fold horizontal seg had: 4-fold seg in z • Acceptance for neutrals (γ, π0, n) from η > 8.1 • (100% for η > 8.4) • Ready for 2008 run Monika Grothe, UW meeting May 29 2008

  44. 3m Test Beam TOTEM T1 & T2 tracking detectors • Gas Electron Multiplier (GEM) • Mounted in front of CASTOR • 5.3 < | < 6.5 • 10 planes formed by 20 GEM semi-circular modules • Radial position from strips, h, from pads • Resolution strip~70mm • Cathode Strip Chambers (CSC) • Mounted in front of HadronForward calorimeter of CMS • 3.1 < | < 4.7 • 5 planes with 3 coordinates/plane • 6 trapezoidal CSC detectors/plane • Resolution  ~ 0.8mm Monika Grothe, UW meeting May 29 2008

  45. Multiplicity and E flow measurements Titel Can differentiate between certain MC tunes to describe underlying event with CASTOR/T2 Can differentiate between MC models for cosmic rays with CASTOR/T2/ZDC Monika Grothe, UW meeting May 29 2008

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