Results, Status and Perspectives for 2010/11. Karsten Eggert on behalf of the TOTEM Collaboration

Transcription

1 Results, Status and Perspectives for 2010/11 Karsten Eggert on behalf of the TOTEM Collaboration Workshop on Hadron Hadron & Cosmic-Ray Interactions at multi-tev Energies ECT* - Trento, Nov 29th Dec 3 rd, 2010 p. 1

2 TOTEM Physics Overview Total cross-section Elastic Scattering b Forward physics Diffraction: soft and hard b jet jet p. 2

3 Experimental IP5 Inelastic telescopes: charged particle & vertex reconstruction in inelastic events T1: 3.1 < < 4.7 T2: 5.3 < < 6.5 T1: mrad T2: 3 10 mrad IP5 HF (CMS) ~ 10 m ~ 14 m T1 CASTOR (CMS) T2 Roman Pots: measure elastic & diffractive protons close to outgoing beam IP5 RP147 RP220 p. 3

4 All T1 Modules Ready in the Test Beam Zone Successfully tested with pion and muon beams in May June Both arms are completely assembled and equipped in the test beam line H8. Both telescope arms ready for installation TOTEM aims at the installation of both T1 telescope arms during the winter technical stop to enable first total cross-section measurements in p. 4

5 efficiency T1 telescope performance Both arms successfully tested with pion and muon beams Pions on copper target to get many-tracks events reconstructed hits CSC efficiencies with muons (triple coincidences) Longitudinal vertex Cu target Transverse vertex Beam monitor frame p. 5

6 T2 Telescope 2 arms of GEMs for tracks and vertex reconstruction 5.2< <6.5 Df=2 Both arms installed and taking data p. 6

7 Installation of half T2 Telescope Half a telescope assembled in lab The GEMs are installed as pairs with a back-to-back configuration. Installation 7

8 The Roman Pot System p. 8

9 Roman Pot detector assembly Roman Pot System All 12 Roman Pots at ±220 m from IP5 are operational: delivering data with active triggers. RP147 detector assemblies to be installed in winter technical stop. Until June: data were taken with RP220 in retracted position. p. 9

10 11/30 p. 10 Units installed into the beam vacuum chamber allowing to put proton detectors as close as possible to the beam Beampipes Edgeless detectors to minimize d Each RP station has 2 units, 5m apart. Each unit has 2 vertical insertions ( pots ) and 1 horizontal Horizontal Pot Vertical Pot BPM

11 p. 11

12 dn ch /d [1/unit] TOTEM: Acceptance Inelastic Acceptance in : non-diffractive minimum bias events: Proton Acceptance in (t, x): (contour lines at A = 10 %) (x = Dp/p) Charged particles per event single-diffractive events: t = p 2 d 2 x = Dp /p All TOTEM detectors have trigger capability. p. 12

13 Overview first T2 run: tracks seen April T2 commissioning with beam, RP comm. in garage position, bunch-crossing trigger first tracks in RPs in garage position, active trigger first T2 data with squeezed optics b * = 2m 2 b., 2e10 p/b RP beam-based alignment 450 GeV, b * = 11m 1 b., 3e10 p/b later 9e10 p/b first T2 data with nominal bunches b * = 3.5m, 1e11 p/b (nom.) RP insertion to 30 s in stable beams 8 nom. b. RP insertion to 25 s (V) and 30 s (H) in stable beams 8 16 nom. b partial RP beam-based alignment 3.5 TeV, 1 nom. b. 1.5 nb -1 first 2 elastic candidates RP loss map measurement to qualify 20 s settings first RP insertion to 20 s (V) and 25 s (H) 16 nom. b. p. 13

14 Overview 2010 (continued) RP insertions to 20 s (V) and 25 s (H) 16 nom. b nb RP beam-based alignment and run at 7 s 1 nom. b nb RP insertions to 18 s (V) and 20 s (H) nom. b nb special run: RPs inserted to 7 s (V) and 16 s (H) pileup-free data for T2 (trigger on pilot) common run RP + T2 1 pilot b. (1e10) + 4 b. x 7e10 p/b. 8.6 nb -1 Total: 25 s 1.5 nb s 185 nb s 3867 nb -1 7 s 9.5 nb -1 p. 14

15 T2 Fully installed, operative and commissioned on data p. 15

16 HF HF 20/30 p. 16 Preliminary studies with Pythia + full Geant detector simulation Work in progress on: - Understanding secondary contribution and smearing effects - Proper tuning of detector performance simulation - Optimization of trk algorithm and selection cuts for improved rejection of secondary charged tracks, - Estimation of systematic uncertainties IP5 Beam Pipe cone at ~ 5.54 (>100 radiation lengths)

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18 400K inelastic events from dedicated run with low proton density bunches. Raw distribution: - No smearing corrections - No efficiency corrections - No secondaries contribution subtraction Work ongoing on unfolding corrections

19 Collimation-Based Roman Pot Alignment w.r.t. the Beam Centre Alignment is the central problem of Roman Pot measurements LHC collimation system produces sharp beam edges used to align Roman Pots and to determine the centre of the beam (same procedure as collimator setup) Collimator cuts a sharp beam RP approaches this produces spike in Beam edge symmetrically to the centre edge until it scrapes Loss Monitor downstream second RP approaches When both top and bottom pots feel the edge: they are at the same number of sigmas from the beam centre as the collimator the beam centre is exactly in the middle between top and bottom pot p. 19

20 ( y(mm Measurement of Forward Diffractive and Elastic Protons: the principle Diffractive protons low = m Hit RP220 elastic scattering high 0 m y ~ y scatt ~ t y 1/2 10 x ~ p/p 10 Detect the proton via: its momentum loss (low ) ( its transverse momentum (high Detector requirements: To approach the beam as close as possible: almost edgeless detectors Reliable movement system with solid mechanical stability for reproducible alignment high resolution of typically 20mm Trigger capability with large flexibility p. 20

21 LHC Optics Large Chromaticity effects p. 21

22 Physics with RP detectors Elastic scattering, s = 7 TeV, β * = 2 m Elastically scattered proton flux RP220 [mb/mm 2 ] 10 σ beam envelope Vertical RPs contain all events s( t ) = GeV 2 ( t ) PPP3, 3 pomeron model: s acc 4 mb s el ~ 20 mbarn p. 22

23 Track map (side 4,5) for left right coincidences t x p. 23

24 Track map (side 5,6) for left right coincidences p. 24

25 Collinearity in q y Low x, i.e. x < 0.4 mm and 2s cut in Dq x * Compatible with the beam divergence p. 25

26 Collinearity in q x Low x, i.e. x < 0.4 mm and 2s cut in Dq y * Q x is measured with 5m lever arm spectrometer Compatible with the beam divergence p. 26

27 26/30 p. 27 Preliminary t-distribution 84K elastic scattering candidate events TOTEM special run (~ 8 nb -1 ) s = 7 TeV b* = 3.5 m 7 s (V) and 16 s (H) Raw distribution: - No smearing corrections - No acceptance corrections - No background subtraction Sys. err. sources under study: alignment, beam position and divergence, background, optical functions, efficiency,

28 t distribution : different models 50 k events in t- range: 2 5 GeV 2 p. 28

29 Elastic Scattering - from ISR to Tevatron ISR ~ 1.7 GeV 2 ~ 0.7 GeV 2 ~1.5 GeV 2 Diffractive minimum: analogous to Fraunhofer diffraction: t ~p 2 q 2 exponential slope B at low t increases minimum moves to lower t with increasing s interaction region grows (as also seen from s tot ) depth of minimum changes shape of proton profile changes depth of minimum differs between pp, pˉp different mix of processes p. 29

30 Total Cross-Section and Elastic Scattering at low t Coulomb scattering Coulomb-Nuclear interference Nuclear scattering ds = dt 4 2 ( c G ( t ( - G ( t f s s ( tot 16 t t ( c 2 tot e - Bt e - Bt/2 4 Optical Theorem: s = ( T ( t = 0) tot elastic, nuclear s TOTEM Approach: = Re / Im T elastic,nuclear (t = 0) Measure the exponential slope B in the t-range GeV 2, extrapolate ds/dt to t=0, measure total inelastic and elastic rates (all TOTEM detectors provide L1 triggers): f = fine structure constant = relative Coulomb-nuclear phase G(t) = nucleon el.-mag. form factor = (1 + t / 0.71) -2 Ls 2 tot 16 dn = 1 elastic, nuclear 2 dt t = 0 Ls tot = N elastic, nuclear N inelastic s tot 16 = 2 1 ( dn / dt ) N elastic, nuclear elastic, nuclear N t = 0 inelastic p. 30

31 Possibilities of measurement ( s) r = 2 p s tot ds ( s) d ln s asymptotic behaviour: 1 / ln s for s pred. ~ 0.13 at LHC tot Try to reach the Coulomb region and measure interference: move the detectors closer to the beam than 10 s mm run at lower s < 14 TeV

32 Measurement of the Inelastic Rate N inel = L s inel Inelastic double arm trigger: robust against background, inefficient at small M Inelastic single arm trigger: suffers from beam-gas + halo background, best efficiency Inelastic triggers and proton (SD, DPE): cleanest trigger, proton inefficiency to be extrapolated Trigger on non-colliding bunches to determine beam-gas + halo rates. Vertex reconstruction with T1, T2 to suppress background Extrapolation of diffractive cross-section to large 1/M 2 assuming ds/dm 2 ~ 1/M 2 simulated Loss at low diffractive masses M Acceptance single diffraction extrapolated detected s [mb] trigger loss [mb] systematic error after extrapolations [mb] Non-diffractive inelastic Single diffractive Double diffractive Double Pomeron Total p. 32

33 Combined Uncertainty in s tot s tot 16p el t= 0 2 r Nel Ni nel 1 dn / dt 2 1+ r ( N ) 2 el + Ninel = + + p dnel / dt t= 0 b * = 90 m 1540 m Extrapolation of elastic cross-section to t = 0: ± 4 % ± 0.2 % Total elastic rate (strongly correlated with extrapolation): ± 2 % ± 0.1 % Total inelastic rate: ± 1 % ± 0.8 % (error dominated by Single Diffractive trigger losses) Error contribution from (1+ 2 ) using full COMPETE error band d / = 33 % ± 1.2 % L = 16 Total uncertainty in s tot including correlations in the error propagation: b * = 90 m : ± 5 %, b * = 1540 m : ± (1 2) %. Slightly worse in L (~ total rate squared!) : ± 7 % (± 2 %). Precise Measurement with b * = 1540 m requires: improved knowledge of optical functions alignment precision < 50 mm p. 33

34 Central Diffraction (DPE) 5-dimensional differential cross-section: 5 d s 1 1 b t b t e 1 1 dt dt d x d x d f x x Any correlations? Mass spectrum: change variables (x 1,x 2 ) (M PP, y PP ): M PP 2 = x 1 x 2 s ; y PP = 1 x ln 1 2 x 2 normalised DPE Mass Distribution (acceptance corrected) 14 mb / GeV d 2 s ( dm dy M 1 s(m) = GeV b * =90m: s(m) = GeV s(m)/m = 2 % 1.4 nb / GeV 50 events / (h cm -2 s -1 sufficient statistics to measure the inclusive mass spectrum p. 34

35 Track distribution for an inclusive trigger (global OR ) Trigger on minibunch Average number of min. bias events per bunch crossing : 0.02 p. 35

36 Single diffraction low x sector 45 IP sector 56 RP T2 T2 RP p. 36

37 Single diffraction large x sector 45 IP sector 56 RP T2 T2 RP p. 37

38 Min. Bias and diffractive events p. 38

39 Double Pomeron Exchange sector 45 IP sector 56 RP T2 T2 RP low ξ high ξ p. 39

40 Expected Results from 2010 Elastic scattering t distribution from GeV 2 Double Pomeron: mass distribution and kinematics Single diffraction: correlation of and rapidity gaps Forward multiplicity distributions Multiplicity correlations over large rapidity gap p. 40

41 Running Strategy for 2011 Repeat RP alignment at nominal conditions to understand new optics approach the RP detectors to the sharp beam edges produced by the LHC collimators This will enable constant running at closer approaches to the beams (~15 s in normal runs improve statistics at large t-values Special runs with several low proton density bunches plus one normal bunch: approach RP to ~ 5 s to reach lowest t around 0.2 GeV 2 Add one low-intensity bunch to the standard bunch train if possible Take data with T2 at reduced pile-up (< 10-2 ) Prepare the b* = 90 m optics measure the total cross-section and luminosity Targets: Approaching the RP closer to the beams enables s tot and s el with b*=90m Rich programme with single diffraction and Double Pomeron Correlations between the forward proton and topologies in T1 and T2 With larger b* ~ m Coulomb region might be accessible p. 41

42 de/d dn ch /d CMS + TOTEM: Acceptance largest acceptance detector ever built at a hadron collider Studies in a new kinematical range might lead to unforeseen discoveries Roman Pots T1,T2 CMS T1,T2 Roman Pots Charged particles ZDC b * =90m RPs CMS T1 T2 central HCal CASTOR CMS Energy flux b * =1540m = - ln tg q/2 p. 42

43 The TOTEM Collaboration Penn State University, University Park Case Western Reserve Univ., Cleveland, Ohio USA Estonian Academy of Sciences, Tallinn, Estonia Academy of Sciences, Praha, Czech Republic CERN, Geneva, Switzerland INFN Sezione di Bari and Politecnico di Bari, Bari, Italy Università di Siena and Sezione INFN-Pisa, Italy MTA KFKI RMKI, Budapest, Hungary University of Helsinki and HIP Helsinki, Finland Università di Genova and Sezione INFN, Genova, Italy p. 43

44 End p. 44

45 p. 45

46 p. 46

47 50 µm Silicon Edgeless Sensor for Roman Pots Planar technology with CTS (Current Terminating Structure) Efficiency at the edge s = 20 µm p. 47

48 Log(-x) Log(-x) Single Diffraction, s = 7 TeV, b* = 2 m SD Pythia distribution [mb] SD accepted protons [mb/mm 2 ] RP220 s = 6.8 mb (per side) Log(-t/GeV 2 ) SD accepted protons RP220 [mb] 20s 10s 10s 20s s = 1.2 mb (per side) Log(-t/GeV 2 ) p. 48

49 Raw Data: Hit Map for Left-Right Coincidences 24/30 p. 49 Side 45 t x x = Dp/p; t = t x + t y ; t i ~ -(pq i *) 2 (x *, y * ): vertex position at IP (q x*,q y* ): emission angle at IP Hits related to elastic scattering candidates Tracks reconstructed in left (45) and right (56) sides

50 Log(-x) Log(-x) Single Diffraction, s = 7 TeV, b* = 2 m SD Pythia distribution [mb] SD accepted protons [mb/mm 2 ] RP220 s = 6.8 mb (per side) Log(-t/GeV 2 ) SD accepted protons RP220 [mb] 20s 10s 10s 20s s = 1.2 mb (per side) Log(-t/GeV 2 ) p. 50

51 Elastic Scattering, s = 7 TeV, b* = 2 m Elastic scattering cross-section KL/PP3 model, subrange of -t > 0.3 GeV 2 Elastically scattered proton flux [mb/mm 2 ] RP220 20s 10s acceptance 15s 20s 10 s beam envelope 10s GeV 2 p. 51

52 p. 52

53 Double Pomeron exchange sector 45 IP sector 56 RP T2 T2 RP low ξ high ξ T2 tracks in sector T2 tracks in sector p. 53

54 Hit distribution for an inclusive trigger (global OR ) p. 54

55 Acceptance for inelastic events (1) Uncertainties in inelastic cross sections large: 5 non-diffractive minimum bias (MB) mb single diffraction (SD) mb double diffraction (DD) 4-11 mb T2 T1 PHOJET s = 7 TeV T1 T2 Low multiplicities in diffraction Accepted event fraction: Efficiency increases p. 55

56 Acceptance Elastic Scattering Acceptances b* = m b* = 1540 m Detector distance to the beam: 10s+0.5mm b*=1540 m b*=90 m -t = 0.01 GeV 2 b*=2 m -t = GeV 2 Beam log(-t / GeV 2 ) Detector distance 1.3 mm 6 mm