1 Forward Physics with CMS Marek Taševský (Univ.Inst. Antwerp) DIS 04 - Štrbské Pleso 16/ Introduction Physics Detectors options Slides by Albert De Roeck (CERN)

2 The Large Hadron Collider (LHC) PP collisions at  s = 14 TeV 5 experiments 25 ns bunch spacing  2835 bunches p/bunch Design Luminosity: cm -2 s cm -2 s -1  100 fb -1 /year 23 inelastic events per bunch crossing TOTEM In LEP tunnel (circonf km) Planned Startup: April 1 st 2007

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

4 Diffraction and Forward Physics TOTEM: TDR submitted in January 2004/ in the process of approval TOTEM stand alone –Elastic scattering, Total pp cross section and soft diffraction. Totem has no central detector TOTEM together with CMS: –Full diffractive program with central activity. TOTEM will be included as a subdetector in CMS (trigger/data stream) CMS: EOI submitted in January 2004: –Diffractive and low-x physics part of CMS physics program –Diffraction with TOTEM Roman Pots and/or rapidity gaps LOI in preparation for new forward detectors (CASTOR, ZDC) –Additional options being studied ATLAS: LOI submitted (March) for RP detectors to measure elastic scattering/ total cross sections/luminosity. Diffraction will be looked at later ALICE, LHCb: no direct forward projects plans but keeping eyes open.

5 The TOTEM Experiment TOTEM physics program: total pp, elastic & diffractive cross sections Apparatus: Inelastic Detectors & Roman Pots (3 stations) CMS IP 147 m215 m - t= t=10 -2 High  * (1540m): Lumi cm -2 s -1 (few days or weeks) >90% of all diffractive protons are seen in the Roman Pots. Proton momentum measured with a resolution ~10 -3 Low  *: (0.5m): Lumi cm -2 s m: 0.02 <  < /400m: <  < 0.2 (RPs in the cold region) 180 m

6 TOTEM/CMS forward detectors T1 T2 TOTEM T2 CASTOR 9,71 λ I T2 T1/T2 inelastic event taggers  T1 CSC/RPC tracker (99 LOI)  T2 GEM or Silicon tracker (TOTEM/New)  CASTOR Calorimeter (CMS/New) T1 3<  <5 T2 5<  < <  < 6.7

7 CMS/TOTEM Study Common working group to study diffraction and forward physics at full LHC luminosity approved by CMS and TOTEM (spring 2002) (ADR/ K. Eggert organizing so far) Use synergy for e.g. simulation, physics studies & forward detector option studies. Common DAQ/Trigger for CMS & TOTEM Discussions on T2 Common simulation etc… Share physics studies Common LOI on diffractive physics (pending LHCC approval) on the time scale of ~1 year CMS/TOTEM is the largest acceptance detector ever built at a hadron collider

8 For the first time at a collider large acceptance detector which measures the forward energy flow 1 day run at large beta (1540m) and L=10 29 cm -2 s -1 : 100 million minimum bias events, including all diffractive processes >90% of all diffractive protons are detected microstation at 19m ? RPs Total TOTEM/CMS acceptance (  * =1540m) CMS/TOTEM is the largest acceptance detector ever built at a hadron collider TOTEM+CMS T1,T2 Roman Pots Charged particles Energy flux CMS/TOTEM Study

9 Forward Physics Program Soft & Hard diffraction –Total cross section and elastic scattering –Gap survival dynamics, multi-gap events, proton light cone (pp  3jets+p) –Diffractive structure: Production of jets, W, J/ , b, t, hard photons –Double Pomeron exchange events as a gluon factory (anomalous W,Z production?) –Diffractive Higgs production, (diffractive Radion production?) –SUSY & other (low mass) exotics & exclusive processes Low-x Dynamics –Parton saturation, BFKL/CCFM dynamics, proton structure, multi-parton scattering… New Forward Physics phenomena –New phenomena such as DCCs, incoherent pion emission, Centauro’s Strong interest from cosmic rays community –Forward energy and particle flows/minimum bias event structure Two-photon interactions and peripheral collisions Forward physics in pA and AA collisions Use QED processes to determine the luminosity to 1% (pp  ppee, pp  pp  ) Many of these studies can be done best with L ~10 33 (or lower)

10 Diffraction at LHC: PP scattering at highest energy Soft & Hard Diffraction  < 0.1  O(1) TeV “Pomeron beams“ E.g. Structure of the Pomeron F( ,Q 2 )  down to ~ & Q 2 ~10 4 GeV 2 Diffraction dynamics? Exclusive final states ? Gap dynamics in pp presently not fully understood! proton momentum loss measured in RPs

11 DPE:  from Di-jet events Et> 100 GeV/2 figs P t >100 GeV/c for different Pomeron structure functions H1 fit 6 H1 fit 5 H1 fit 4 (x 100) (1-x) 5 x(1-x) H1 fit 6 d  (pb)events  High  region probed/ clear differences between different Pomeron SFs   =  jets E T e -  /(  s  ) ;  from Roman Pots; E T and  from CMS (using POMWIG generator)

12 H gap -jet  Diffractive Higgs Production Exclusive diffractive Higgs production pp  p H p : 3-10 fb Inclusive diffractive Higgs production pp  p+X+H+Y+p : fb p p beam p’ roman pots dipole ~New: Under study by many groups Advantages Exclusive:  Jz=0 suppression of gg  bb background  Mass measurement via missing mass E.g. V. Khoze et al M. Boonekamp et al. B. Cox et al. …

13 MSSM Higgs Kaidalov et al., hep-ph/ fb 1fb SM Higgs: (30fb -1 ) 11 signal events O(10) background events Cross section factor ~ 10 larger in MSSM (high tan  ) Also: Study correlations between the outgoing protons to analyse the spin-parity structure of the produced boson  See talk of A. Martin

14 Beyond Standard Model Diffractive production of new heavy states pp  p + M + p Particularly if produced in gluon gluon (or  ) fusion processes Examples: Light CP violating Higgs Boson M H < 70 GeV B. Cox et al. Light MSSM Higgs h  bb at large tan  Light H,A (M<150 GeV) in MSSM with large tan  (~ 30)  S/B > 10 Medium H,A (M= GeV) medium tan  ? V. Khoze et al. Radion production - couples strongly to gluons Ryutin, Petrov Exclusive gluino-gluino production? Only possible if gluino is light (< GeV) V. Khoze et al.

15 SM Higgs Studies Needs Roman Pots at new positions 320 and/or 420 m Technical challenge: “cold” region of the machine, Trigger signals… Curves: Helsinki Group Dots: Fast sim. using DPEHIGGS MC model Mass of Higgs

16 Diffractive Higgs Production Mass resolution vs. central mass from protons measured in roman pots assuming  x F /x F = Exclusive channel pp  p H p advantages Good mass resolution thanks to missing mass method:  M = O( ) GeV (including systematics) Study possible in the b-quark decay mode b-quark background suppression: (J Z =0 states)!!  Switch of dominant background (at LO)! Inclusive production pp  p+X+H+Y+p : 100 x larger cross section but background not suppressed (gain under study) and missing mass less effective Mass resolution (GeV) Central Mass (GeV) symmetric case:

17 Detectors at 300m/400m Detectors in this region requires changes in the machine Physics Case –Can we expect to see a good signal over background?  Signal understood (cross section) ?  Needs good understanding of the background (inclusive!)  Needs more complete simulations (resolutions, etc.) Trigger –300m/400m signals of RPs arrive too late for the trigger  Can we trigger with the central detector only for L1? Note: L1 2-jet thresholds E T > ~150 GeV Machine –Can detectors (RPs or microstations) be integrated with the machine? Technically there is place available at 330 and 420 m Of interest for both ATLAS and CMS Some Major Concerns:

18 Detectors at 300/400m News since Manchester meeting Intervention in the cold section unpopular (with machine) –Personal opinion: unlikely to happen before LHC startup –Will need a serious proposal this year: ATLAS+CMS+… Study of M. Boonekamp et al. shows –Not possible to make use of final state gaps  lumi will be too low –S/B in previous studies was too optimistic  significance (30fb -1 ): 3   –However mass resolution used in Boonekamp et al study too pessimistic (did not take into account  correlations (K. Osterberg)) Topological triggers on final state jets & activity for H  bb and H  being studied by Helsinki/Wisconsin using full CMS trigger software. Results expected soon (so far hopeful). Investigate to increase mass resolution (1-2 GeV) even more…difficult! Investigate other ways to accept these protons, e.g. using a different optics. Discussions starting with the machine. Try to increase acceptance at lower masses In all, the SM Higgs may not be sufficient enough reason for RP’s in the cold region.

19 Low-x at the LHC LHC: due to the high energy can reach small values of Bjorken-x in structure of the proton F(x,Q 2 ) Processes:  Drell-Yan  Prompt photon production  Jet production  W production If rapidities above 5 and masses below 10 GeV can be covered  x down to Possible with T2 upgrade in TOTEM (calorimeter, tracker) 5<  < 6.7 ! Proton structure at low-x !! Parton saturation effects?

20 Low-x at the LHC Rapidity ranges of jets or leptons vs x range |  |<55<|  |<7 7<|  |<95.5<|  |<7.8 Kimber Martin Ryskin Log 10 (x) Shadowing corrections for different saturation radii R

21 Di-jets in pp scattering jet  Azimuthal decorrelation between the 2 jets versus rapidity distance between the 2 jets Large  range needed Rise? Measurements for low-x (BFKL) dynamics

22 High Energy Cosmic Rays Interpreting cosmic ray data depends on hadronic simulation programs Forward region poorly known/constrained Models differ by factor 2 or more Need forward particle/energy measurements e.g. dE/d  … Cosmic ray showers: Dynamics of the high energy particle spectrum is crucial

23 Relative luminosity S  = L  /L pp: : ~ 0.1% for W> 200 GeV Must tag protons at small |t| with good resolution: TOTEM Roman Pots! Process WWA spectrum Reach high W  values!! Two-photon interactions at the LHC p p CMS Totem K. Piotrzkowski Double tags All events Elastic events

24 Two-photon interactions at the LHC p p New studies:  p interactions with x  Luminosity Sensitivity to Large Extra Dimensions

25 SM HIGGS case Number of Higgs events for single tags and assuming integrated lumi-nosity of 30, 0.3 and 0.03 fb -1 for pp, pAr and ArAr collisions, respectively. Significant production rates and very clean signatures available - both transverse and longitudinal missing energy Exclusive production! Range up to GeV for single tags SUSY K. Piotrzkowski

26 Status of the Project Common working group to study diffraction and forward physics at full LHC luminosity approved by CMS and TOTEM (spring 2002) (ADR/ K. Eggert organizing) Use synergy for e.g. simulation, physics studies & forward detector option studies. Some of this happened e.g. RP & T2 simulation, detector options Detector options being explored –Roman Pot/microstations for beampipe detectors at 150, 215, add 310 & 420 m ? (cold section!) –Inelastic detectors T1 CSC trackers of TOTEM (not usable at CMS lumi) Replace T2 with a compact silicon tracker (~ CMS technology) or GEMs Add EM/HAD calorimeter (CASTOR) behind T2 Add Zero degree calorimeter (ZDC) at 140 m Common DAQ/Trigger for CMS & TOTEM Common simulation etc…

13570 Tungsten and quartz plates Length 152 cm~ 9 I Electromagnetic section 8 sectors/ needs extension APD detectors A calorimeter in the range 5.3 <  < 6.7 (CASTOR) A Forward Calorimeter (CMS) T2 CASTOR Position of T2 and Castor (7/2/03)

28 Beam pipe splits 140m from IR ZDC LOCATION BEAMS “Spectators” ZDC ZDC Tungsten/ quartz fibre or PPAC calorimeter EM and HAD section Funding pending in DOE ZDC: zero degree calorimeter M. Murray

29 Opportunities for present/new Collaborators CMS central detector –Diffractive Gap Trigger (possible in CMS trigger but needs to be studied) T2 region –Calorimeter (CASTOR) Add  granularity (silicon, PPAC,…) Castor trigger So far only one side of CMS equipped (500 kCHF) –T2 tracker (part of TOTEM, but still in flux…) May need participation from CMS (if silicon option) May need new tracker by CMS (if GEM option)… watch TOTEM TDR Detectors at 300/400m –Completely new project –Needs new resources (there are interested parties in CMS & ATLAS) ZDC small project but funding not yet garanteed New detectors in the range 7<  <9??? (20 m from IP)  Certainly help welcome on simulation tools, detailed physics studies…

30 Rapidity Gaps at LHC Number of overlap events per bunch crossing versus LHC lumi distribution of nr. of int. per bunch crossing ` 1 int. in 22% 1 int. in 4% Doable at startup luminosity without Roman Pots!

31 Summary A study group has been formed to explore the common use of CMS and TOTEM detectors and study the forward region. –Physics Interest - Hard (& soft) diffraction, QCD and EWSB (Higgs), New Physics - Low-x dynamics and proton structure - Two-photon physics: QCD and New Physics - Special exotics (centauro’s, DCC’s in the forward region) - Cosmic Rays, Luminosity measurement, (pA, AA…) –Probably initial run at high  * (few days/weeks  pb -1 ) –Runs at low  * ( fb -1 ) NEW: CMS officially supports forward physics as a project! –Expression of interest for the LHCC –Opportunities for present/new collaborators to join  complete forward detectors for initial LHC lumi However: Contribution to LOI needed NOW