Frigyes Nemes (Eötvös University) on behalf of the TOTEM collaboration

Transcription

1 Frigyes Nemes (Eötvös University) on behalf of the TOTEM collaboration Hadron Structure' , 29 June 4 July Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 1

2 Total cross-section TOTEM Physics Elastic Scattering b Forward physics Diffraction: soft (and hard with CMS) jet jet Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 2

3 Experimental layout T1: 3.1 < h < 4.7 T2: 5.3 < h < 6.5 IP5 10 m 14 m T1 T2 CASTOR (CMS) IP5 m m m RP147 RP220 Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 3

4 The inelastic telescope T1 Properties: installed inside CMS at 7.5 to 10.5 m from IP5 there is one telescope on each side of IP5 each telescope consists of two quarters the quarters are formed by 5 equally spaced planes the planes contain 3 trapezoidal CSC detectors, each covering 60 in azimuth Cathode Strip Chamber: gaseous detector with 3 read-out coordinates (at 60 wrt. each other) Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 4

5 The T2 inelastic telescope Properties: installed inside CMS shielding between HF and Castor calorimeters centered around 13.5 m from IP5 there is one telescope on each side of IP5 each telescope contains two quarters each quarter formed by 10 semi-circular planes, assembled in 5 back-to-back mounted pairs each plane equipped with a Gas Electron Multiplier detector gaseous detector, electron multiplication by 3 perforated foils (2 mm separation) radial segmentation: strips (resolution 0.15 mm) Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 5

6 1 RP station: 2 units at about 5 m distance measurement of very small proton scattering angles (few µrad) vertical and horizontal pots mounted as close as possible to the beam BPM fixed to the structure gives precise position relative to the beam overlapping detectors: relative alignment (10 µm inside unit between 3 RPs) Roman Pot stations RP unit: 2 vertical, 1 horizontal pot + BPM Horizontal RP 3.5 cm Vertical RPs BPM 10 planes of edgeless detectors Si edgeless detector 1 Roman Pot Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 6

7 LHC Optics Essential for TOTEM physics! The relevant magnet lattice: Proton transport description IP5 Roman Pots Proton position at a given RP (x, y) is a function of (x*, y*) and angle (Q x*, Q y* ) at IP5 Measured RP IP5 and reconstructed proton kinematics Θ * y y L y Θ * x dl ds x 1 Θ x d x ds x * Machine imperfections alter the optics: Strength conversion error, σ(b)/b 10-3 Beam momentum offset, σ(p)/p 10-3 Magnet rotations, beam harmonics, Perturbed element δl y,b1 /L y,b1 [%] MQXA.1R MQXB.A2R Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 7

8 Optics optimization Optics estimation based on: MAD-X MAD-X based Monte-Carlo Measured optical function ratios from Roman Pots Matching Optimized Measurement F. Nemes, H. Niewiadomski, LHC Optics Determination with Proton Tracks IPAC'12, Louisiana, USA, Spread due to imperfections Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 8

9 Physics results Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 9

10 Elastic scattering Elastic tagging: s = 7 TeV, β* = 3.5 m Topology, collinearity cuts [EPL 95 (2011) 41001] Collinearity Θ x Spread in agreement with beam divergence (17-18 μrad) Collinearity Θ y Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 10

11 TOTEM first elastic dσ/dt result After acceptance corrections, unfolding, inefficiency corrections, luminosity: t range spans from 0.36 to 2.5 GeV 2 below t = 0.47 GeV 2 exponential e -B t behavior dip moves to lower t, proton becomes larger GeV 2 : power low behavior t -n pp elastic Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 11

12 Several model descriptions: the data show a strong discriminative power Model predictions & fits Bourrely model & Petrov model: the slope B t =0.4 GeV2, t dip and the exponent n at large t are consistent with the data not consistent with the cross-section dσ/dt in the measured range other models are less consistent The measured dσ/dt compared with predictions of several models B (t=-0.4 GeV 2 ) t DIP t -N [ GeV 2 ] [GeV -2 ] [GeV 2 ] Islam Jenkovsky Petrov Bourrely Block TOTEM 23.6 ± 0.5 ± ± 0.01 ± ± 0.3 ± 0.1 Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 12 [N]

13 Low-t measurement, cross-sections Properties: β* = 90 m excellent agreement between the two measurements with different optics The exponential slope B confirms that it increases with s: B Extrapolation to t = 0: Integral elastic cross-section: Total cross-section (with optical theorem): d dt el 2 tot inel GeV 20 stat syst t0 ( mb 16 c 2 1 tot extrapol. 2 el d dt el stat 16.5 mb t syst measured ) mb GeV 0.14 stat syst mb stat 1.2 tot syst mb EPL 96 (2011) stat 2.8syst mb Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 13

14 t min = GeV 2 at 7 TeV RP@ 10 σ beam size@rp 6.5, 5.5, 4.8 σ beam size@rp ) EPL 101(2013) Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 14

15 Extrapolation to t = 0 Slope parameter: B GeV 19 stat syst Extrapolation: d dt t0 ( stat syst ) mb GeV -2 Elastic cross section: el stat 1.07syst mb 91 % is measured EPL 101(2013) Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 15

16 Inelastic cross-section measurement Trigger: at least one track in T2 95 % of inelastic events 1. Raw rate: event counting with T2 Experimental corrections: trigger and reconstruction inefficiencies, beam-gas event suppression, pile-up 2. Visible rate: visible with T2 in perfect conditions Estimation of events with no tracks in T2: T1-only events, events with gap over T2, low-mass diffraction EPL 101 (2013) Physics rate: true rate of inelastic events only one major Monte-Carlo-based correction: low-mass diffraction (which can be constrained from data) inel = 73.7 ± 3.4 mb Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 16

17 σ tot with 4 methods At s=7 TeV: 1. Low luminosity (CMS) + Elastic d/dt + Optical th. ( EPL 96(2011) ) depends on CMS luminosity for low-l bunches, elastic efficiencies and on ρ 2 tot 16 c High luminosity (CMS) + Elastic + Optical theorem (EPL 101 (2013) 21002) 3. High luminosity (CMS) + Elastic + Inelastic (EPL, 101 (2013) 21004) minimizes dependence on elastic efficiencies and no dependence on ρ tot el 4. Elastic ratios + Inelastic ratios + Optical theorem (EPL, 101 (2013) 21004) Eliminates dependence on luminosity dn EL 2 16 c dt t0 tot 2 1 N N 2 inel d dt el EL t0 INEL tot = 98.3 ± 2.8 mb tot = 98.6 ± 2.2 mb tot = 99.1 ± 4.3 mb tot = 98.0 ± 2.5 mb Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 17

18 Luminosity independent cross-sections s=8 TeV β* = 90 m CERN preprint: CERN-PH-EP Accepted by PRL Elastic, inelastic, total cross-sections σ tot [mb] σ el [mb] σ inel [mb] ± ± ± 1.7 Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 18

19 Hadronic-Coulomb interference at 8 TeV Analysis aim: Measure dσ el /dt at the smallest possible proton t (where the Coulomb interaction can be probed): Coulomb + Hadronic + Interference Determination of ρ: Re Im d dt A A H H t0 A C H 2 Further improve the total cross-section σ tot measurement TOTEM Preliminary The relevant data set: s = 8 TeV, β* = 1000 m RP at 3 σ beam t min = GeV 2 Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 19

20 Hadronic-Coulomb interference at 8 TeV Extraction of ρ and σ tot by fitting the Hadronic-Coulomb interference region: Error bars include: Fit statistical uncertainty The effect induced on the fit by the relevant experimental uncertainties (misalignment, normalization,..) stat syst model Green line + band: 8 TeV σ tot measurement (β* =90m, luminosity independent): Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 20

21 Forward and diffractive physics Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 21

22 All the drawings show soft interactions. In case of hard interactions there should be jets, which fall in the same rapidity intervals. Inelastic and Diffractive Processes 60 mb Elastic Scattering 25 mb Single Diffraction Double Diffraction M 10 mb 5 mb Measure (M,,t) Double Pomeron Exchange M 1 mb << 1 mb Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 22

23 dn ch /dh dn ch /dη measured with T2, s=7 TeV Very forward measurement with T2 : Published EPL, 98 (2012) Visible cross section measured on data: ~ 94% σ inel Diffractive mass M diff > 3.4 GeV Combined with other LHC exp. Main contributions to the systematical error: Subtraction of secondary particles. Track efficiency Misalignment uncertainties Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 23

24 CMS+TOTEM common dn ch 8 TeV Very forward measurement with T2 : CMS vertex information is used to reduce the pile-up correction Both CMS and TOTEM analysis obtained triggering with T2, on the same events Same CMS-TOTEM event selection (at least a track reconstructed in T2) Measurements are representative for an inelastic event sample with at least a primary charged particle with p t >40 MeV/c produced in the range 5.3 < η < 6.5 Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 24

25 Diffractive physics Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 25

26 Soft Single Diffractive cross-section 7 TeV =Dp/p Low mass diffraction ( < ξ < 10-6 ) Tracks in the T2 hemisphere opposite to the proton RP RP sector 45 IP sector 56 h T2 T2 sector 45 IP sector 56 T2 T2 RP Very high mass ( ξ > 2.5 % ) RP Rapidity Gap Dh = -ln SD events are triggered with T2, only 1 proton required in RP M obtained from the rapidity gap estimation based on charged track η in T1 and T2 Δη= - ln(m 2 /s). This allows a better ξ resolution (σ(ξ)/ξ ~ 1) for low medium mass Rapidity Gap Dh = -ln M X 2 = s M X 2 = s h h 7 7 Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 26

27 Soft Single Diffractive cross-section 7 TeV d C e dt Bt Corrections included: Trigger efficiency Reconstruction efficiency Proton acceptance Background subtraction Extrapolation to t = 0 Missing corrections: ξ resolution Beam divergence effects Estimated uncertainty: B ~ 15 %, σ ~ 20 % Very preliminary result: σ SD = 6.5 ± 1.3 mb 3.4 < M SD < 1100 GeV Very-high masses: ongoing Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 27

28 Soft Double Diffractive cross-section at 7 TeV Event selection: Trigger with T2, at least one track in both T2 hemispheres, no tracks in T1 (0T1+2T2) topology Aim: Measurement of soft double diffractive cross-section with particle η min visible to TOTEM T2 ( 4.7 < η min < < M diff < 8 GeV) ND background estimated scaling the MC prediction using a control sample from data dominated by ND (2T1+2T2 events) SD background estimated completely from data using a SD-dominated control sample (0T1+1T2) with protons in the RP Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 28

29 Soft Double Diffractive cross-section at 7 TeV Results from 7 TeV data: Preliminary the σ DD uncertainty is dominated by events with η min outside detector acceptance 120 h DD( 4.7 min 6.5) 25 b MC comparisons: Improvement expected with the 8 TeV data, including also the CMS information Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 29

30 Central Diffraction (or DPE) TOTEM alone Correlation between leading protons and forward detector T2: sector 45 IP sector 56 RP T2 T2 RP 2 =Dp 2 /p 2 1 =Dp 1 /p 1 low ξ high ξ Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 30

31 Central Diffraction TOTEM alone Available data s=7 TeV and β* = 90m optics: trigger selection: 2 RP nearly complete ξ-acceptance background: elastic, beam-halo + inelastic elastic: anti-elastic cuts, or use forbidden topologies (top-top, bottom-bottom) beam-halo: y > 11 σ beam halo is negligible B= GeV -2 TOTEM Preliminary 2 d dt dt 1 CD CD 2 σ CD estimation: C( D dt dt 2 1,2 ) e 1 Bt 2 d dt dt 2 1 CD e Bt 2 1mb Single arm CD event rate in RP integrated, acceptance corrected Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 31

32 Central Diffraction TOTEM+CMS Unprecedented properties: Mass of diffractive system X is double determined By TOTEM Roman Pots M X = s ξ 1 ξ 2 By CMS Double arm proton detection Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 32

33 Central Diffraction TOTEM+CMS TOTEM + CMS = unprecedented rapidity coverage: CMS tracker : η < 2.5 CMS calorimeters : η < 5.5 TOTEM T1 : 3.1 < η < 4.7 TOTEM T2 : 5.3 < η < 6.5 CMS FSC : 6 < η < 8 Available data s = 8 TeV, β* = 90 m CMS and TOTEM is consistent within resolution M CMS (particle flow) = M TOTEM p CMS (particle flow) = p TOTEM Low cross-section processes: Background critical (pile-up) More data needed Pile-up removal 0 or 1 vertex in CMS RP near edge area removed (1 elastic proton + beam halo or SD) ξ > 1.5 % RP ξ predicts event topology in central detectors FSC empty: QCD background protection M X,CMS < M X,RP Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 33

34 Central Diffraction TOTEM+CMS Run / Event : / β* = 90 m Jets E T = 65, 45, 27 GeV p T (CMS) = 3.4 GeV FSC empty both sides ξ - = -0.1, ξ + = M(pp) = 244 GeV M CMS = 219 GeV Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 34

35 Total cross-section Summary Elastic Scattering b Measured at 7 and 8 TeV Measured at 7 and 8 TeV < t < 2.5 GeV 2 Forward physics Diffraction: soft (and hard with CMS) Preliminary results DD, CD, SD Many analysis in progress! jet jet Forward multiplicity distribution 7 and 8 TeV Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 35

36 TOTEM Consolidation & Upgrade program Present : LHC in LS1 Restart : 2015 at s=7 TeV even higher luminosities higher pile-up TOTEM interest to lower cross-section processes higher lumi. pile-up How to deal with pile-up? two units will be replaced hosting rotated (or pixel) detectors multiple tracks can be resolved association of TOTEM and CMS tracks : two new units hosting timing detectors RP147: relocated to m longer arm better angular resolution 1 unit rotated by 8 degrees Other upgrade activities: RP impedance optimization reduce heating reduce feedback on beam Secondary particle / shower production studies Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 36

37 Thank you for your attention! Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 37

38 Backup slides Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 38

39 t y -acceptance corrections t <0.36 GeV 2 excluded from analysis Missing acceptance in θ y * due to beam divergence Correction error (t y ): 0.31 GeV 2 : 30% 0.33 GeV 2 : 11% 0.35 GeV 2 : 2% 0.4 GeV 2 : 0.8% 0.5 GeV 2 : 0.1% Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 39

40 Accepted (t) ϕ-acceptance corrections Θ * Diagonal Total -acceptance correction No. t [GeV 2 ] Θ * [rad] Accepted (2 diag.) [ ] accept. correct. factor E ±4.7% E ±1.8% E ±0.3% E ±0.1% E E Accepted (t) Diagonal 2 t <0.36GeV 2 excluded from analysis Critical at low t-acceptance limit Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 40

41 Uncorrected dn/dm Uncorrected dn/d 1,2 Differential DPE distributions (uncorrected) -distribution RP reconstruction alone proton 45 proton 56 Uncorrected dn/dt 1,2 t-distribution 1,2 >3% all 1,2 proton 45 proton 56 acceptance loss acceptance difference 1,2 M-distribution -t [GeV 2 ] 1,2 >3% Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM s 1 [GeV] 41 M 2