Early forward physics and diffraction at the LHC: - Physics scenarios for TOTEM & CMS Risto Orava Division of High Energy Physics, Department of Physical Sciences University of Helsinki and Helsinki Institute of Physics TOTEM Collaboration Goals, Signatures, Experimental lay-out, Performance, Exclusive DPE Higgs... Forward Proton Taggers at the LHC Manchester June 9th 2004
Additional forward coverage opens up new complementary physics program at the LHC • Investigate QCD:stot, elastic scattering, soft & hard diffraction, multi- rapidity gap events (see: Hera, Tevatron, RHIC...) • Studies with pure gluon jets: gg/qq… • Gluon density at small xBj • Gap survival dynamics, multi-gap events, proton light cone (pp3jets+p) • Diffractive structure: Production of jets, W, J/, b, t, hard photons, • Parton saturation, BFKL dynamics, proton structure, multi-parton scattering • Search for signals of new physics based on forward protons + rapidity gaps Threshold scan for c,b (Higgs…) states in: pp p+X+p  • Extension of the ‘standard’ physics reach of the CMS experiment into the forward region • Luminosity measurement with DL/L 5 % Khoze,Ryskin,Martin & Stirling
WHAT IS DIFFRACTION? p p ? p p Experimentally: A process causing rapidity gaps that are not exponentially suppressed.... R.Orava
A POMERANCHUK? ”Pomeron” exchange R.Orava
TWO-GLUON EXCHANGE? R.Orava
REGGE LADDER? . . . R.Orava
FLUCTUATING GLUON VACUUM! IN DIFFRACTION WE PROBE THE HADRONIC VACUUM. R.Orava
Even Elastic Scattering Remains Unclear... Coulomb scattering: ds/dt 1/t2 logs Coulomb&Strong Inteference: r ? hard soft Multigluon (”Pomeron”) exchange exp(Bt) ”Structure” pQCD 0.001 0.8 |t| (GeV/c)2 Region |t| [GeV]2Running Scenario Coulomb region 510-4 [lower s, measurement closer to beam] Interference, r meas. 510-4510-3 [as above], standard b* = 1540 m Pomeron exchange 510-3 0.1 b* = 1540 m Diffractive structure 0.1 1b* = 1540 m, 200 - 400 m (?) Large |t| – perturb. QCD 1 10 b* = 18 m Rapidity gap survival & ”underlying” event structures are intimately connected with a geometrical view of the scattering - eikonal approach!
Photon - Pomeron interferencer Pomeron exchange (~exp Bt) diffractive structure pQCD Ldt = 1033 & 1037 cm2 Studying elastic scattering requires special LHC optics. These will yield large statistics in a few days. ds/dt (mb/GeV2) (* = 1540 m & 18 m)
Ldt = 1033 1037 cm-2 27.103/GeV2 15/GeV2 -t(GeV2) Elastic scattering measurements can be extended to large –t. Large t scattering 1 eff.day (105sec) at high b and 18 m ds/dt (pp) (mb/GeV2)
Total cross section will be measured with high precision. • Historical : CERN Tradition (PS-ISR-SPS) • Dispersion relation fit (logs)g, g=2.20.3 • Current models predictions: 100-130mb • Aim of TOTEM: ~1% accuracy • Absolute calibration of Luminosity TOTEM
Elastic and inelastic rates allow the pp luminosity to be determined independently and with good precision. Luminosity relates the cross sectionsof a given process by: L = N/s A process with well known, calculable and large s (monitoring!) with a well defined signature? Need complementarity. Measure simultaneously elastic (Nel) & inelastic rates (Ninel), extrapolateds/dt 0, assumer-parameter to be known: (1+r2) (Nel + Ninel)2 L = 16p dNel/dt|t=0 Ninel = ? Need a hermetic detector. dNel/dtt=0 = ? Minimal extrapolation to t0: tmin 0.01
Single Diffractive Excitation is characterized by a leading proton, a rapidity gap and a diffractively excited hadronic system. p1* p1 Signatures: Leading Proton Forward Jet & Rapidity Gap = 1 - xF = M2/s P p2’ p2 1 V.A.Khoze,A.D.Martin and M.G.Ryskin, hep-ph/0007359 ds/dh p2’ proton:p2’ diffractive system:p1* rapidity gap h = ln(2pL/pT) hmin 0 hmax hmin hmax ln(2pL/pT) -ln Cross section: d2ssd/ddt = (A/)bexp(-bt) with b~10 GeV-2, t ~ 2p2 Dh lnMdiff2 Gap survival Underlying event structure Parton configurations within the proton
T2 opens up low-x physics at the LHC LHC: Due to the high energy, small values of Bjorken-x are available. For rapidities above 5 and masses below 10 GeV x down to 10-6 ÷ 10-7 Possible with T2 in TOTEM (calorimeter, tracker): 5 < < 6.7 Q2 Proton structure at low-x: Parton saturation effects? D-Y, jets,W, saturation? Saturation or growing proton? J. Stirling in HELA-LHC ws -04
”Pomeron” structure function can be determined from the SDE processes and compared to the measurements at HERA & Tevatron • The standard approach: ”Pomeron” emitted from a beam proton with an associated Pomeron ”flux”. Pomeron interacts with other beam proton with sPp (Ingelman&Schlein). A useful - but not theoretically sound – paradigm! • Use the Pomeron “structure function” measured at HERA (g-P collisions) and/or Tevatron (P-p collisions) for predictions at the LHC: If the quasi-elastically scattered proton is measured, the –t and (=Dp/p < 0.05) of the Pomeron is known together with the proton xF (= 1-Dp/p 0.95). • Production of high ET jets, W’s, Z’s, Drell-Yan pairs, heavy flavour seen and measured at the Tevatron with typical cross sections of the order of 1% of the corresponding total cross section. • By measuring two high ET jets in P-p collisions, can reconstruct the momentum fractions of the proton (xBj) and Pomeron (b) • ”Pomeron structure function” R.Orava
- - p p P x p Study the diffractive structure function Regge factorization: The Diffractive Structure Function Subject of interest: Hard diffraction process: production of high pT dijets Single Diffractive dissociation
CDF – Diffractive Di-jets exhibit a “factorization breaking” expected from the different parton configurations and kinematics in ep vs. pp • The diffractive structure function measured using SD dijet events at the Tevatron is smaller than that at HERA by approximately an order of magnitude. • The discrepancy can be explained by rap gap non-survival (ref. KMRS) CDF Collaboration, Phys. Rev. Lett. 84, 5043-5048 (2000).
Example: Di-Jet production Reach in and • Jet cross sections/events generation • with POMWIG generator • Cuts: 0.001<<0.1 and |t|<1GeV2 • Pt > 10, 100 GeV/c • ||<5 (CMS acceptance) • Roman pot acceptance • 200m: 0.02<<0.1 • 400m(?): 0.002<<0.1 • (low lumi use rapidity gaps) b = Bjorken-x of parton in the Pomeron Albert de Roeck
Rapidity Gap Signature identifies colour singlet exchange processes Non-diffractive interactions: rapidity gaps induced through multiplicity fluctuations. Diffractive interactions: rapidity gaps induced by colour singlet exchange • From Poisson statistics: • P(Dh) = exp(-rDy) • (r = dn/dy = particle density in rapidity space) • Gaps are exponentially suppressed. proton diffractive system rapidity gap -ln hmax ln(2pL/pT) ds/dM2 1/M2ds/dDy constant Large rapidity gaps (2-3 units) are signatures of diffraction.
x : Momentum Loss Fraction can be evaluated by using the diffractive mass. Measure fractional momentum loss of the proton MX 2 x = Recoil p s S ET e-h x = s Dy= ln (1/x) Diffractive events are boosted towards positive h small x
Double Diffractive Excitation is characterized by two diffractively excited systems with a rapidity gap in between. p1* p1 Signatures: 2 Forward Jets & Rapidity Gap P p2* p2 ds/dh diffractive cluster: p2* diffractive cluster:p1* rapidity gap h2min h2max h1min h1max h2min h2max h1min h1max h
Double Pomeron Exchange produces two leading protons, two rapidity gaps and a central hadronic system. In the exclusive process, the background is suppressed and the central system has selected quantum numbers. Measure the parity P = (-1)J: ds/d 1 + cos2 p1’ p1 P MX212s JPC = 0++ (2++, 4++,...) P p2’ Mass resolution S/B-ratio p2 2p Gap Jet+Jet Gap diffractive system proton:p1’ proton:p2’ 0 hmin h hmax rapidity gap rapidity gap hmin hmax R.Orava 1 V.A.Khoze,A.D.Martin and M.G.Ryskin, hep-ph/0007359
Soft Diffraction measurements at the Tevatron require adjustments in “Pomeron flux”… CDF/ Dino Goulianos et al. SD DD σ (mb) DPE SDD Gap Fraction
The mass of X in p1p2 p1’ + X + p1’ can be measured as: MX2 = (p1 + p2 – p1’ – p2’)2 by using energy -momentum conservation jet 1 - how accurate are you? CMS p1’ p2’ -beam energy spread? jet 2 - transverse vx position? • leading protons on both sides (roughly symmetric) • (aim at protons down to a of 1,2 1%o) • a central system in CMS separated by rap gaps - will return to this later!
Signatures • Proton • elastic proton (b*=1540m, b*=200m & 400m) • diffractive proton (b*=1540m, b*=200m & 400m, b*=18m) • hard diffractive proton (b*=0.5m) • Rapidity Gap • soft diffractive rap gap (L < 1033cm-2 s-1) • hard diffractive rap gap ( L~ 1033cm-2 s-1) • multiple gaps (2, 3,...) (L < 1033cm-2 s-1) • Very Fwd Objects • Jets? • g, e, m ? • tracks (vx constraints?, pattern recognition?) • ? • Correlation with CMS Signatures(central jets, b-tags,...) R.Orava
Correlation with the CMS Signatures • e, g, m, t, and b-jets: • tracking: |h| < 2.5 • calorimetry with fine granularity: |h| < 2.5 • muon: |h| < 2.5 • Jets, ETmiss • calorimetry extension: |h| < 5 • High pT Objects • Higgs, SUSY,... • Precision physics (cross sections...) • energy scale: e & m 0.1%, jets 1% • absolute luminosity vs. parton-parton luminosity via • ”well known” processes such as W/Z production? R.Orava
TOTEM Physics Scenarios Proton b* (m) rapidity gap L(cm-2s-1) inelastic activity jet g,e,m,t L, D++,... TOTEM & CMS TOTEM & CMS TOTEM & CMS elastic scattering 1540 18 beam halo 1028 -1032 total cross section 1540 1028 -1033 acceptance soft diffraction 1540 200-400 gap survival L, K±, ,... 1029 -1031 mini-jets? 200-400 0.5 jet acceptance central & fwd W, Z, J/,... hard diffraction 1031 -1033 200-400 0.5 di-jet backgr central pair b-tag, g, J/,... DPE Higgs, SUSY,... 1031 -1033 200-400 0.5 mini-jets resolved? central & fwd jets di-leptons jet-g,... low-x physics 1031 -1033 exotics (DCC,...) p± vs. po multiplicity jet anomalies? leptons g’s,...? 0.5 1031 -1033 R.Orava
Trigger • Elastics • left-right • SDE • single-side-proton • single-side-rap gap • single-side-proton and high pT object • DD • activity on both sides and central rap gap • DPE • left-right-protons and some central activity • left-right-rap gaps and some central activity • Inelastics • standard CMS triggers • non-elastics/non-diffractive and fwd activity
Need: • Leading Protons • Extended Coverage of Inelastic Activity • CMS
Need to Measure Inelastic Activity and Leading Protons over Extended Acceptance in , , and –t. Measurement stations (Roman Pots) at locations optimized vs. the LHC beam optics. LP1 LP2 LP3 147 m 180 m 220 m Measure the deviation of the leading proton location from the nominal beam axis () and the angle between the two measurement locations (-t) within a doublet. Acceptance is limited by the distance of a detector to the beam. Resolution is limited by the transverse vx location (small ) and by beam energy spread (large ).
Beampipes Roman Pots allow precision detectors to be placed within a few mm’s from the LHC beam. Strict environmental controls are required. Measurement of very small p scattering angles (few mrad): Leading proton detectors in RPs approach beam to 10s + 0.5mm1.5 mm 2004 prototype 3D detectors by C.DaVia et al.
The acceptance of leading protons depends on the location and reach of the detectors within the pots. b* = 1540 m
At high b* nearly all the diffractive protons are seen. Luminosity 1028-1030cm-2s-1 (few days or weeks) • more than 90% of all diffractive protons are seen! • proton momentum can be measured with a resolution of few 10-3
total beam angular divergence = 0 Good resolution in t & allows forward-backward collinearity selection and additional physics studies. (t)/t vs detector resolution resolution vs t All performace plots based on LHC6.4 optics using MADX simulation. All relevant smearings at IP & RP locations taken into account. Test collinearity of protons with 2 arms Background reduction Use correlation for DPE selection
CMS tracking is extended by forward telescopes CMS T1-CSC: 3.1 < h < 4.7 T2-GEM: 5.3 <h< 6.5 T3-MS: 7.0 <h< 8.5 ? Totem1 Totem2 10.5 m CASTOR ~14 m Totem3? ~19 m - a microstation at 19m is an option
T1 – DETECTOR: LAYOUT ALUMINIUM FRAME/SUPPORT HALF DETECTOR SUB-ASSEMBLY TWO HALF DETECTORS ALLOW INSTALLATION WITH THE VACUUM CHAMBER IN PLACE. ALUMINIUM FRAME FOR EACH CSC PLANE (SUPPORTS ELECTRONICS, SERVICES AND LINK TO THE RAILS) THE TRUSS/RAIL SYSTEM IS INTEGRAL PART OF DETECTOR CSC PLANE SUB-ASSEMBLY
T2 Telescope is based on GEM Chambers 5.3< lhl < 6.7 Vacuum Chamber 1800 mm 400 mm Bellow Castor Calorimeter(CMS) T2 GEM Telescope: 8 planes 13500 mm from IP
Totem T2 – GEM Fwd inelastic activity 3-foil structure • 16 semi-circular GEMs form 8 planes • two GEMs of each plane overlap • a 50 cm long telescope @ 13.5 m requires • a spatial resolution of 70-100 mm • Rates: 50 Hz/cm2 @ L = 1028 • 50 KHz/cm2 @ L = 1031 • Aging performance: 10mC/mm2 The group has long term experience on GEM’s
Totem GEM 2D prototype for the beam test in 2004 Readout structure 256 equidistant strips (80mm wide, 400mm pitch) 64(j) x 24(h) = 1536 pads (2x2 mm2 __ 7x7 mm2) Part of Compass DAQ (NIM A 490 (2002) 177) Based on technology developed for COMPASS frame spacer 3-foil structure Beam test from August -04 HV services Analogue readout of the strips via APV25 GEM sector border
t=0 extrapol. error Inelastic error 1% Accuracy of stot Trigger Losses (mb) Vertex extrapolation simulated extrapolated Acceptance detected F. Ferro
Microstation Inch worm motor Emergency actuator Inner tube for rf fitting 6cm Space for encoder Space for cables and cooling link Detector Note: The secondary vacuum arrangement not shown. 3D detectors by C.DaVia et al. 3D-detectors
Microstation - initial design • 3 generations of prototypes • now with a secondary vacuum 2.6
Total TOTEM/CMS acceptance (b*=1540m) RPs microstation at 19m? Important part of the phase space is not covered by the generic designs at LHC. TOTEM CMS Covers more than any previous experiment at a hadron collider. Charge flow information value low: - bulk of the particles crated late in space-time leading protons leading protons Energy flow information value high: - leading particles created early in space-time TOTEM + CMS In the forward region (|h > 5): few particles with large energies/small transverse momenta.
Running Scenarios 1 - low b* physics will follow...
p p p Level-1 trigger schemes (L = 1.6 x 1028 cm-2 s-1) RP CMS RP Elastic Trigger: Signal: 500 Hz Background: 20 Hz Single Diffractive Trigger: Signal: 200 Hz Background: < 1 Hz ? (using vertex reconstruction in T1/T2) Double Diffractive Trigger: Signal: 100 Hz Central Diffractive Trigger: Signal: 10 Hz Background: 2 Hz Minimum Bias Trigger: Signal: 1 kHz Backgrounds under study! T1/T2 p p
Existing TOTEM Studies - Mostly on (signature) performance • Elastic acceptance & resolution for b*=1500m • Matti Järvinen (Kenneth, Valentina, Stefan) • Diffractive acceptance for b*=1500m • Erik Goussev (Kenneth, Valentina) • Extrapolation to t=0 (b*=1500m) • Matti Järvinen (Kenneth, Valentina, Mario, Stefan) • Inelastic rate measurement & stot accuracy • Fabrizio Ferro (Marco et al.) • Diffractive acceptance & resolution for b*=0.5m • central DPE mass resolution • Tuula Mäki (Niko, Juha, Mikael, Kenneth, Stefan) • Trigger studies for DPE (b*=0.5m) • Ville Bergholm (Kenneth, Stefan) R.Orava
Ongoing TOTEM Studies • Elastic acceptance & resolution for b*=400/200/18 m • Diffractive resolution for b*=1500 m • Diffractive acceptance & resolution for b*=400/200/18 m • r-parameter measurement (b*=xxx m) • Measurements at lower s • Measurements of final state properties in forward region • (partonic) structure of diffraction • Resonance production R.Orava