1 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 1 The Pomeron as little helper in tracking down the Higgs ? - Forward Physics at the LHC Monika Grothe U Turin/ U Wisconsin German Physical Society Spring Meeting Dortmund March 2006 Central exclusive production: What is it and why is it interesting ? The FP420 project Diffraction and fwd physics with CMS/Totem/FP420

2 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 2 Suppose you want to detect a light SM Higgs (say M H =120 GeV) at the LHC... 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 Vacuum quantum numbers “Double Pomeron exchange” shields color charge of other two gluons Central exclusive production pp  pXp Suppression of gg  jet jet because of selection rules forcing central system to be (to good approx) J PC = 0 ++

3 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 3 The physics interest of CEP Selection rules result in the central system being (to good approx) J PC = 0 ++ I.e. a particle produced with proton tags has known quantum numbers Excellent mass resolution (~GeV) from the protons, independent of the decay products of the central system CP violation in the Higgs sector manifests itself as azimuthal asymmetry of the protons Proton tagging may be the discovery channel in certain regions in the MSSM “A glue-glue collider where the beam energy of the gluons is known and at which central 0 ++ states are produced.” Central exclusive production pp  pXp Vacuum quantum numbers “Double Pomeron exchange” shields color charge of other two gluons

4 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 4 The physics interest of CEP Detecting a light SM Higgs at the LHC b b H Vacuum quantum numbers “Double Pomeron exchange” In CEP background reduced dramatically because: of excellent mass resolution of J Z selection rule: to accuracy (m b /E t ) 2 only J PC = 0 ++ states produced Models can be tested at Tevatron run II (CEP of  c,b, dijets) b jets : M H = 120 GeV  = 2 fb (uncertainty factor ~ 2.5) M H = 140 GeV  = 0.7 fb M H = 120 GeV : 11 signal / O(10) background in 30 fb -1 after detector cuts WW * : M H = 120 GeV  = 0.4 fb M H = 140 GeV  = 1 fb M H = 140 GeV : 8 signal / O(3) background in 30 fb -1 after detector cuts Cross section calculations by Khoze, Martin, Ryskin (also other models available) shields color charge of other two gluons

5 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 5 The physics interest of CEP MSSM: intense coupling regime Intense-coupling regime of the MSSM: M h ~M A ~ M H ~ O(100GeV): their coupling to, WW*, ZZ* strongly suppressed  discovery very challenging at the LHC Cross section of two scalar (0+) Higgs bosons enhanced compared to SM Higgs Production of pseudo-scalar (O-) Higgs suppressed because of J Z selection rule Superior missing mass resolution from tagged protons allows to separate h, H Spin-partity of Higgs can be determined from the azimuthal angles between the two tagged protons (recall J Z rule only approximate)  CEP as discovery channel see Kaidalov et al, hep-ph/0307064, hep-ph/0311023 100 fb 1 fb 120 140  10 fb

6 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 6 “3-way mixing” scenario of CP-violating MSSM: the 3 neutral Higgs bosons are nearly degenerate, mix strongly and have masses close to 120 GeV Superior mass resolution from tagged proton allows disentangling the Higgs bosons by measuring their production line shape Explicit CP-violation in Higgs sector manifests itself as asymmetry in the azimuthal distribution of tagged protons (interference of P- and P+ amplitudes) (Khoze et al., hep-ph/0401078)  CEP as CP and line-shape analyzer ! The physics interest of CEP MSSM: CP violation in the Higgs sector J. Ellis et al., hep-ph/0502251 120 124 Hadronic level cross section when Higgs bosons decay into b bbar, for different values of mixing angles

7 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 7 Detecting CEP of a light Higgs: Necessary ingredients beam p’ roman pots dipole Proton spectrometer using the LHC beam magnets: Detect diffractively scattered protons inside of beam pipe It has been done before, for example UA2+UA8 @SPS/CERN, LPS @ZEUS/HERA, Forward proton detectors currently in use at D0

8 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 8 CEP of a light Higgs: Necessary ingredients (II)  =0 (beam)  =0.002  =0.015  1  2 s = M 2 With √s=14TeV, M=120GeV on average:   0.009  1% With nominal LHC optics: Nominal LHC beam optics Low  * (0.5m): Lumi 10 33 -10 34 cm -2 s -1 @220m: 0.02 <  < 0.2 @420m: 0.002 <  < 0.02  fractional momentum loss of the proton

9 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 9 CEP of a light Higgs: Necessary ingredients (III) Detectors at 420m - challenging:  420m is in the cold region of the LHC  420m is too late for the CMS/ATLAS L1 trigger, i.e. need to trigger with central apparatus and/or RPs closer to the IP FP420 TOTEM or corresp. ATLAS detectors Detectors at 420m complement acceptance of 220m detectors needed to extend acceptance down to low  values, i.e. low M Higgs Detectors at ~220m needed in addition to optimize acceptance (tails of  distr.) can be TOTEM RP detectors and/or, after upgrade, RP detectors of ATLAS luminosity system

10 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 10 The FP420 project At 420 m after ATLAS/CMS IP diffractively scattered protons emerge between the two beam pipes, which are at 1.9K Need “near-beam” movable detectors, integrated with cryostat Submission to the LHCC in June 2005: “FP420: An R&D proposal to investigate the feasibility of installing proton-tagging detectors in the 420m region at LHC” M. Albrow et al., CERN-LHCC-2005-025 LHCC reaction: “The LHCC acknowledges the scientific merit of the FP420 physics programme and the interest in exploring its feasibility” See www.fp420.comwww.fp420.com

11 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 11 The FP420 project (II)  R&D project with ATLAS and CMS members  Once/if feasibility established could be built at ATLAS and/or CMS  Installation: not before the first long LHC break, ie no interference with LHC startup  Funding for R&D program secured  Test beams in summer 2006 at Fermilab and CERN (mechanics, detectors)  Take decisions based on R&D work by the end of 2006 Aim for NIM paper in spring 2007 Construction could start by the end of 2007 Ingredients: LHC cryostat redesign Development of detectors Development of appropriate detector insertion mechanism  Most likely scenario: Cryogenic bypass with 15m cold-warm transition, warm beam pipes, detectors at room temp  Forerunner for detector technology: edgeless 3D Silicon  Insertion mechanism under disc.: Roman pots, movable beam-pipe, microstations

12 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 12 After the glamour - now the bread-and-butter forward and diffractive physics 2 gluon exchange with vacuum quantum numbers “Pomeron” X Double Pomeron exchange: X Single diffraction: o) If X = anything – then dominated by soft physics; contributes to pile-up, i.e. soft events that overlay signal events at LHC (3.5 @ 10 33 cm -2 s -1, 35 @ 10 34 cm -2 s -1 ) Inclusive Single Diffraction (SD)  15 mb, Double Pomeron Exchange (DPE)  1 mb 1 mb = 100 events/s @ 10 29 cm -2 s -1 X is measured in the central CMS apparatus Scattered protons may be visible in Roman Pot detectors along beam line Note large rapidity gap(s) between the scattered proton(s) and X o) If X includes jets, W’s, Z’s, Higgs (!): hard processes, calculable in QCD. Give info on proton structure, QCD at high parton densities etc (see eg hep-ph/0511047 for a recent review)

13 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 13 Diffractive PDFs: probability to find a parton of given x in the proton under condition that proton stays intact – sensitive to low-x partons in proton, complementary to standard PDFs GPD jet  hard scattering IP dPDF Generalised Parton Distributions (GPD) quantify correlations between parton momenta in the proton; t- dependence sensitive to parton distribution in transverse plane When x’=x, GPDs are proportional to the square of the usual PDFs Looking at the proton through a lens that filters out everything but the vacuum quantum numbers QCD- diffractive PDFs and GPDs

14 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 14 Forward detectors at the LHC Atlas detectors: Lumi: LUCID Cerenkov counters & Roman pots with Silicon fiber detectors on 2 sides at 240m ZDC at 140m CMS/Atlas IP T1/T2, Castor, BSC ZDC RPs@150m RPs@220m LUCID or 240m detectors@420m TOTEM detectors: T1 (CSC) in CMS endcaps T2 (GEM) in shielding behind HF T1 + T2: 3 ≤ || ≤ 6.8 Roman pots with Si detectors on 2 sides at up to 220 m CMS detectors along beam line: Cal with || ≤ 3, HF with 3 ≤|| ≤ 5 Castor calorimeter, behind T2 Beam Scintillation counters BCS Zero-degree calorimeter ZDC Possible addition FP420: Detectors at 420 m in cold region of LHC Selection of diffractive events with rapidity gap selection only possible at luminosities below 10 33 cm -2 s -1, where event pile-up is absent

15 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 15 Proton tagging with TOTEM TOTEM FP420 TOTEM: An approved experiment at LHC for measuring  tot and  elastic, uses same IP as CMS TOTEM’s trigger and DAQ system will be integrated with those of CMS, i.e. common data taking CMS + TOTEM possible 220m detector loc. optimal for special optics runs (*=1540m) @ 10 28 - 10 29 cm -2 s -1 TOTEM suggests few days of running with *=90m @ 10 31 cm -2 s -1, with much improved coverage for diffractive events compared to *=0.5m (@ 10 33 - 10 34 cm -2 s -1) x L =P’/P beam =  At nominal LHC optics (*=0.5m): diffractive peak - fractional momentum loss of proton t - 4-momentum transfer squared from proton K.Eggert, Blois 05 proceed.

16 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 16 Low lumi Rapidity gap selection possible HF, Castor, BSCs, T1, T2 Proton tag selection optional RPs at 220m and 420 m Diffraction is about 1/4 of  tot High cross section processes “Soft” diffraction Interesting for start-up running Important for understanding pile-up High lumi No Rapidity gap selection possible Proton tag selection indispensable RPs at 220m and 420 m Central exclusive production Discovery physics: Light SM Higgs MSSM Higgs Extra dimensions Gamma-gamma and gamma-proton interactions (QED) Forward energy flow - input to cosmics shower simulation QCD: Diffraction in presence of hard scale Low-x structure of the proton High-density regime (Color glass condensate) Diff PDFs and generalized PDFs Diffractive Drell-Yan CMS alone CMS with Totem and/or FP420 Map to diffraction and fwd physics in CMS Low lumi High lumi

17 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 17 Summary  CMS+FP420: Unique advantages of hunting the Higgs with central exclusive production:  excellent mass resolution  determine quantum numbers of produced state from azimuthal distribution of observed protons  SM: light Higgs observable in WW and b bbar modes with S/B ~1  MSSM: proton-tagging friendly in certain regions S/B~20 and CEP would even be discovery channel at the LHC; CEP “may offer unique possibilities for exploring Higgs physics in ways that would be difficult or even impossible in inclusive Higgs production”, J. Ellis  Unique access to a host of interesting QCD processes (p structure, low-x...)  Rich program of and p physics  CMS+TOTEM: Interesting diffractive and forward physics program at more moderate luminosities

18 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 18 Last words... “QCD at a hadron collider is always a ghetto, and there the worst neighborhood is diffraction.” - W.Smith Now the Pomeron is even socializing with the Higgs crowd. We are on the way to respectability ! FWD proton taggers add to the discovery potential of the LHC, by making it possible to capitalize on the unique advantages of central exclusive production.

19 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 19 Latest Acceptance + Resolution P. Bussey / A. Pilkington / J. Monk 420-420 420-220 ATLAS CMS 420-420

20 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 20 Beam-Scintillation counters: One with almost complete phi coverage in front of HF, in addition paddles HF FP420/Totem: FP420: An R&D project, in close collaboration with the LHC machine group and acknowledged by the LHCC, to assess the feasibility of integrating off-momentum particle detectors 420 m downstream of ATLAS and/or CMS Installation as phaseII detectors, after first long LHC shut-down Totem: An approved exp. for measuring  tot and  elastic, uses same IP as CMS “Near” detectors:

21 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 21 Proposal submitted to LHCC last June 58 authors 29 institutes Authors from: ATLAS, CMS, TOTEM CDF, D0, LHC Close collaboration with ATLAS and CMS Contacts: B. Cox (Manchester, ATLAS) A. De Roeck (CERN, CMS)

22 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 22 The physics interest of CEP Detecting a light SM Higgs at the LHC SM Higgs with ~120 GeV: gg  H, H  b bbar mode has highest BR But signal swamped by gg  b bbar Best bet with CMS: H  , where in 30 fb -1 S/√B  4.4

23 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 23 The physics interest of CEP Detecting a light SM Higgs at the LHC (II) Production cross section times branching ratio for CEP From implementation of KMR model in Exhume MC

24 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 24 The physics interest of CEP MSSM: intense coupling regime 100 fb 1 fb Azimuthal angle between outgoing protons sensitive to Higgs spin-parity: J P =0 + vs J P =0 - (recall J Z selection rule only approximate)     Kaidalov et al., hep-ph/0307064

25 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 25 The physics case for FP420 QCD and the structure of the proton FP420 acceptance covers 0.002

26 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 26 The physics case for FP420 Photon-Photon interactions Tag two protons   interactions (K. Piotrzkowski, PRD 63 071502) 2- production of W pairs: studies of quartic gauge couplings  WW  = 110 fb with  M   > 300 GeV  ~ 1000 evts in lept. channels (30 fb -1 ) Sensitivity to anomalous quartic couplings significantly better than LEP2 limits (no other way at LHC to have such sensitivity) Tag a single proton   p interactions Eg W boson production at high transverse momentum top pair production via photon-gluon fusion p p

27 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 27 Technical aspects of FP420 Connection cryostat Near-beam detectors: Edgeless 3-D Silicon Trigger

28 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 28 FP420 technical aspects: Connection cryostat At 420 m after P1 and P5 an off- momentum proton lies between the two beam pipes, which are at 1.9 K Beam protons Δp/p beam = 0.011 % 10 σ beam ≈ 3mm Off-momentum proton Δp = 0.5 % Δx = 10 mm i.e. still inside the 44 mm diameter beam-pipe Need “near-beam” moveable detectors, integrated with cryostat Most likely scenario: Cryogenic bypass with 15m cold-warm transition, warm beam pipes, detectors at room temp Insertion mechanism under disc.: Roman pots, movable beam-pipe, microstations,...

29 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 29 FP420 technical aspects: 3D edgeless Silicon Other advantage of 3D Si: rad hard Use ATLAS pixel chip (rad hard) for readout

30 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 30 FP420 technical aspects: Fast TOF detectors Put at back of 420m (220m?) tracking high precision timing counters. Eg.Quartz Cerenkov + ~ Microchannel PMT  tested (Japanese Gp)  10 ps = 3mm!! Check that p’s came from same interaction vertex (& as central tracks) tLtL tRtR x tLtL tRtR z_ vtx z t Know position in each bunch of interacting p’s. Position-momentum correlation  Reduce uncertainty in incoming momenta. t _int Potentially valuable e.g. MSSM triplet (Higher cross section & close states)

31 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 31 The difficulty of triggering on a light Higgs < 100 Hz < 100 kHz 40 MHz collision High-Level Trigger HLT Level-1 trigger Calo Muon no tracking! The difficulty of triggering on a light Higgs, e.g at 120 GeV: L1 jet trigger signature: 2 jets in CMS Cal, each with E T < 60 GeV  Measured L1 jet E T on average only ~60% of true jet E T  L1 trigger applies jet E T calibration and cuts on calibrated value  Thus: 40 GeV (calibrated) ~ 20 to 25 GeV measured  Cannot go much lower because of noise  Use rate/efficiency @ L1 jet E T cutoff of 40 GeV as benchmark L1 2-jet rate for central jets (||

32 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 32 Triggering on a light Higgs: Central detector jet trigger H T condition = isolation condition for jets: 2 jets in central Cal (|| threshold H T = scalar sum of E T of all jets in the event with E T (jet)>threshold --> Provides factor ~2 rate reduction ECAL HCAL PbWO4 crystal  veto patterns Trigger tower  4x4 trigger towers = region  Search for jets with a sliding 3x3 regions window  Jet = 3x3 region with local energy max in middle  Reconstructed L1 jet E T on average ~ 60% of real jet E T, thus need for jet E T calibration  Jet = 144 trigger towers, with typical jet dimensions:  x = 1 x 1

33 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 33 Triggering on a light Higgs: Single-sided 220 m condition  Very good reduction of rate in absence of pile-up  However, reduction decreases substantially in the presence of pile-up which contains ~30% diffractive events Achievable total reduction: 10 x 2 (H T cond) x 2 (topological cond) = 40 single-sided 220m condition without and with cut on  Can win additional factor ~2 in reduction when requiring that the 2 jets are in the same  hemisphere as the RP detectors that see the proton Jet isolation criterion

34 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 34 Triggering on a light Higgs: 220m and 420m conditions For H (120 GeV, CEP)  b bbar, adding L1 conditions on the RPs at 220m is likely to provide a rate reduction sufficient to meet the CMS L1 bandwidth limits at luminosities up to 2x 10 33 cm -1 s -1 To go even further up in luminosity need additional handle to stay within bandwidth limits... So what about triggering with the 420 m RPs ? At the current CMS L1 latency of 3.2 s they are too far away from IP for inclusion in L1 Note: This is a hardware limit - cannot be changed without replacing trigger pipelines of CMS tracker and preshower detectors with deeper ones Should this however happen (under discussion for SLHC: L1 latency 6.4 s, determined by ECAL pipeline depth) then....

35 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 35 Triggering on a light Higgs: Asymmetric 220/420m condition Require hits on one side in 220m RPs and on one side in 420m RPs In effect means on opposite sides: events where  values of 2 protons are very different Can be used either in L1 after increase in L1 latency, or on HLT For H (120 GeV, CEP)  b bbar, adding L1 conditions on the RPs at 220m and 420m would provide a rate reduction sufficient to meet the CMS L1 bandwidth limits at luminosities up to 10 34 cm -1 s -1 See www.cern.ch/grothe/heralhc/heralhc.ps All results are preliminary

36 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 36 Triggering on a light Higgs: Summary Goal: Define trigger table for a dedicated diffractive trigger stream with target output rates of 1 kHz out of 100 kHz total on L1 and 1 Hz out of 100 Hz total on HLT  Triggering on CEP of a light Higgs with a rap gap trigger is not an option in the presence of pile-up  Can trigger with the central detector alone by using the muon trigger Efficiencies with already foreseen CMS L1 thresholds: 10% for H(120GeV)  b bbar, 20% for H(140GeV)  WW*  Can also use the L1 jet trigger when combining it with RP condition Requires defining a new CMS trigger stream Efficiencies around 10%

37 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 37 Status of the FP420 project Project goal is to establish the feasibility of Modifying the cryostat at 420m – produce design that satisfies the machine and allows insertion of detectors with appropriate mechanics Operating edgeless detectors (eg 3D Si pixel detectors) Being able to trigger and retain sufficient signal acceptance All of the above, with no interference with LHC, ATLAS, CMS, TOTEM Estimated time for this: early 2007 Once/if feasibility established: ATLAS and CMS members of FP420 will go back to their collaborations, propose the addition – then, if accepted, collaboration(s) will submit TDR Installation: not before the first long LHC break – ie no interference with machine startup

38 Monika Grothe, Forward Physics at the LHC, Dortmund March 2006 38 Status of the FP420 project (II) First meeting at FNAL in April 2005 Green light for UK funding (100 k£ seedcorn) Submitted proposal to the LHCC in June; M. Martinez referee LHCC reaction: “The LHCC acknowledges the scientific merit of the FP420 physics programme and the interest in exploring its feasibility” Accelerator interface issues, including redesign of 420m cryostat, funded by UK (Cockroft Institute) Funding of other groups (B, US, I…) being discussed New funding bid in UK in March 2006: design and construction of prototype cryostat, development of the 3D detectors and electronics Test beams in spring and summer 2006 at Fermilab and CERN (mechanics, detectors) Take decisions based on R&D work by the end of 2006 Aim for NIM paper in spring 2007 Construction could start by the end of 2007