TOTEM Status Report & First Measurement of the Total Cross-Section LHCC Open Session – 07 December 2011 S.Giani CERN – CH [on behalf of the TOTEM.
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TOTEM Status Report & First Measurement of the Total Cross-Section LHCC Open Session – 07 December 2011 S.Giani CERN – CH [on behalf of the TOTEM collaboration] OUTLOOK 1. TOTEM experiment, LHC special runs, TOTEM data 2. Total, Elastic, and Inelastic cross-sections 3. Perspectives on diffractive physics & cross-sections 4. Measurement of dN/dh with T2 telescope TOTEM EXPERIMENT, LHC SPECIAL RUNS, TOTEM DATA TOTEM Physics Overview Total cross-section Elastic Scattering b Forward physics Diffraction: soft (and hard with CMS) jet jet 4 Experimental Setup @ IP5 Inelastic telescopes: charged particle & vertex reconstruction in inelastic events T1: 3.1 < h < 4.7 T2: 5.3 < h < 6.5 IP5 HF (CMS) ~ 10 m ~ 14 m T1 CASTOR (CMS) T2 Roman Pots: measure elastic & diffractive protons close to outgoing beam IP5 RP147 RP220 T1 T2 RP 147 Detectors • T1 and T2 detectors are installed and fully operational • 220 m Roman Pot Silicon detectors are fully operational • 147 m Roman Pot detectors are installed and tested Runs & Data Statistics TOTEM pp Elastic differential cross-section s = 7 TeV RP @ 7s Oct 2010 TOTEM vs Models s = 7 TeV Comparison [EPL 95 (2011) 41001] A special run: 1st run with the b* = 90 m optics and RP insertion June 2011 Un-squeeze from injection optics b* = 11m to 90m [Helmut Burkhardt, Andre Verdier] Request of TOTEM (2005) Very robust optics with high precision • • • • • • • Two bunches with 1 and 2 x 1010 protons / bunch Instantaneous luminosity: 8 x 1026 cm-2 s-1 Integrated luminosity: 1.7 mb-1 At the end of machine Estimated pile-up: ~ 0.5 % development Vertical Roman Pots at 10 s from beam center Trigger rate : ~ 50 Hz 0.5 hours data taking by TOTEM Recorded events in vertical Roman Pots: 66950 TOTAL, ELASTIC, AND INELASTIC CROSS-SECTIONS Cross-Section Formulae Optical Theorem: s 2 TOT Using luminosity from CMS: s TOT 16 c ds EL 2 1 dt 2 t 0 ds EL 1 dN EL ; and from COMPETE fit: dt L dt ds EL 19.20 mb GeV dt 0.1400..01 08 2 s TOT s EL s INEL t 0 “Raw Data” Jun’11 – Vertical RPs@10s Sector 56 t = -p2 q2 x Dp/p b*= 90 m Ly ~ 260 m Lx ~ 0-3 m Sector 45 Integrated luminosity : 1.65 mbarn-1 Inel. pile-up ~ 0.005 ev/bx Luminosity & Normalization • Run no.: 5657 (except files 0, 1, 2) • Integrated Luminosity: 1.65103 mb-1 Optics principles • Only lattice between IP5 and RP220 of interest: RP147 RP220 – 6 quardupole magnets (Q1-Q5) – Dipoles, correctors, drift spaces • Optics is defined by the lattice elements Ti, for e.g. – focusing magnet transport matrix: cosl k 1 / k sin l k k sin l k cosl k TF 0 0 0 0 – drift space and dipole matrix: TDrift 1 0 0 0 l 1 0 0 0 0 1 0 0 0 l 1 0 0 cosh l k k sinh l k 0 0 , 1 / k sinh l k cosh l k k – magnet strength, l – length output prot. input prot. x2 x1 x,2 x ,1 y TF y 2 1 y,2 y ,1 Real optics • In reality, due to machine imperfections, the transport matrix of each element can be ‘altered’ by DTi • Tolerances and imperfections leading to DTi – – – – – Beam momentum offset (Dp/p = 10-3) Magnet transfer function error, IB, (DB/B = 10-3) Magnet rotations and displacements (D < 1mrad, Dx, Dy < 0.5mm, WISE database) Power converter errors, kI, (DI/I < 10-4) Magnet harmonics (DB/B = O(10-4) @ Rref = 17mm, WISE database) • Final transport matrix is a product of all the components (Ti + DTi) TIP 5 RP 220 vx dv x 1 ds Ti ki DTi re 31 iM re41 Lx dLx ds re32 re42 re13 re23 vy dvy ds re14 re24 Ly dLy ds DTi – magnet imperfections – values needed for prot. reconstr. – The elements of TIP5RP220 are extensively correlated and cannot take arbitrary values – Measurements of some of the elements constrain the values of the others – Moreover, TOTEM uses 2 beams independently more constraints • Therefore, the TOTEM measurements can infer an ‘effective’ value for Ti’ b*=3.5m real optics estimation • Certain ratios of TIP5RP220 elements are measured directly with proton tracks in Roman Pots – 3 values per beam: dLx dLy ds , ds and Ly Lx Ly re14 – with elastic scattering (Beam 1 = Beam 2), TOTEM can, in addition, relate the optics of Beam 1 and Beam 2, by measuring Ly , Beam1 Ly , Beam 2 dLx , Beam1 ds and dLx , Beam 2 ds • Finally, the 2 minimisation (‘effective’ vs. ‘altered’) is employed to find the highest likelyhood DTi values (together with their variance V) which fulfil the measurements systematics and the machine tolerance constraints • The errors of the estimated optical functions (dLx/ds, Ly) are computed by 1 propagation of V through TIP 5RP220 Ti ki DTi : dLx ds 0.7%, dLx ds iM Ly Ly 1% • The MC studies and the pulls distribution have confirmed the obtained errors b*=90m optics precision estimation – RP optics measurments are in perfect agreement with nominal values • no improvements needed • nominal values of the optical functions used for the reconstruction – Errors estimated on the basis of the machine tolerance – Main errors: Beam momentum offset and magnet transfer function error Error propagation Nominal optics at 220 m Param. bx by μx μy vx Lx Nominal optics 313 m 770 m π π/2 -1.87 0.0 m dvx/ds dLx/ds vy Ly dvy/ds dLy/ds 0.056/m -0.536 0.0 263 m -0.0038 /m 4.74 Magnet transfer function error propagation [σk)/k = 0.1%] MQXA 0.23% 0.28% 0.01% -0.30% 0.11% Inf. 0.16% -0.40% Inf. 0.14% -6.78% 0.14% MQXB -0.12% -0.46% -0.01% 0.42% -0.06% Inf. -0.07% 0.29% Inf. -0.23% 9.35% -0.24% MQXB -0.11% -0.50% -0.01% 0.41% -0.06% Inf. -0.06% 0.38% Inf. -0.25% 9.19% -0.26% MQXA 0.18% 0.41% 0.03% -0.28% 0.09% Inf. 0.10% -0.96% Inf. 0.20% -6.23% 0.21% MQY 0.02% -0.02% 0.00% 0.00% 0.01% Inf. 0.00% 0.00% Inf. -0.01% 0.03% -0.01% MQML -0.21% 0.08% 0.00% 0.00% -0.10% Inf. 0.15% 0.06% Inf. 0.04% -0.07% 0.09% Inf. -0.16% 0.71% Inf. 0.01% -5.38% 0.07% Inf. 0.30% 1.34% Final syst. errors Beam momentum error propagation [σ(p)/p = 0.1%] 0.02% 0.03% -0.02% -0.25% 0.01% Total of syst. errors per beam (in square): 0.39% 0.85% 0.05% 0.76% 0.20% Inf. 0.43% 16.90% 0.45% – Ly = 263m is particularly stable since it is close to 220 m (with all quadrupoles off) Optics Control 56 dLx/ds Ly [m] RP215 RP220 D RP215 D RP220 -0.311962 -0.311962 -2.84% -2.84% 45 dLx/ds Ly [m] RP215 RP220 D RP215 D RP220 -0.314508 -0.314508 -4.51% -4.51% 34 33 22.1464676 22.6191755 +0.78% +0.81% 35 36 2 31 2/NDF = 25.8/(36-26)=2.6 ROT [mrad] 20.3883272 0.0400268 20.6709463 0.0372828 +10.19% +10.79% 1 2 3 4 (would be lower if correlations are eliminated) Mean pull = 0.043 Pull RMS = 0.86 Full nonlinear fitting with harmonics and displacements. 1 25 5 1.5 32 ROT [mrad] Strong correlations between fitted parameters 0.0432331 Principle Component Analysis (PCA) should ideally 0.0396463 be applied. Anyway results checked with MAD-X. 24 6 7 1 30 0.5 28 11 26 12 25 13 24 14 23 15 22 21 20 19 18 17 16 4 5 22 10 27 3 1 6 9 0 2 1.5 23 8 29 26 2 0.5 All constraints 21 7 Fitted parameters 0 20 8 19 9 18 10 17 11 16 15 14 13 12 Optics and t-scale • Perturbations: optics very robust, better than: – DΘx*/Θx*=1.3%syst – DΘy*/Θy*=0.4%syst • Non-linearities in Θx*(y) reconstruction due to dLx/ds fixed: (checked via Lx) • t systematics: Dt/t = 0.8% (low t) up to 2.6% Elastic Tagging Q*x = 1 æ dvx * ö Q ×x ÷ dLx ç x è ø ds ds q*x ‘resolution’ includes also the detector and the vertex spread in plot above, but vertex effect vanishes when computing q with elastic constraint Q*y= y Ly q*y resolution (very large Ly) in agreement with beam divergence sQ = * en = 2.4mrad gb * Acceptance Correction • Effect of the cumulative acceptance correction in both dimensions Correction factor Acceptance corrected t-distr. Efficiency Detector + Tracking • Method: 3 pots out of 4 Accept. + eff. cor. Near bottom 56: 1.3% • • • • Far top 45: 3.3% Diag. top56 bot. 45: 1.5+2.5+1.4+3.3+(1.5+2.5)(1.4+3.3) = 8.9% Diag. bot. 56 top 45: 1.3+2.7+1.4+3.1+(1.3+2.7)(1.4+3.1)= 8.7% Uncorrelated 2 pots out of 4 taken into account Not observed far-far or near-near correlations Detector and tracking efficiency > 91% Data Reduction & Trigger • Analysis of full data reduction starting from number of triggers (u .or. v , near .or. far , 45 .or. 56) shows very clean data • Confirmed results of efficiency calculations • No additional correlated inefficiencies • Negligible inefficiency near-far same arm Overall trigger efficiency limit : > 99.9% Background Subtraction • Extrapolation of the background of the EPL paper should be an upper limit (2SD + DPE +…) for the real contamination of the low t-distribution: found to be <=1% @ |t|<0.1 GeV2 y* (proton1) - y* (proton2)] / √ 2 The data confirm that there is no measurable background. Plots above: left: before colinearity req.; middle: after colinearity req.; right: no tails Resolution Unfolding Correction function, DB=0.11 t-distribution accept. + eff. +unfolded s *x 1.7 2 (frombeam div.) 42 (det.res.) 4.4μrad s *y 1.7μrad (frombeam div.) Monte Carlo method (acceptance cuts for different resolution in x and y) Low-t Elastic Differential Cross-Section Consistency with EPL95(2011)41001 TOTEM: pp Elastic Cross-Section B = 20.1 GeV -2 Exponential slope: B t 0 20.1 GeV 2 Extrapolation to t = 0: ds dt 5.037 10 2 mb / GeV 2 t 0 Integral Elastic Cross-Section σ EL 8.3 mb (extrapol.) 16.5 mb (measured) 24.8 mb Systematics and Statistics • • • • • t : [0.6:1.8]%syst optics <1%align. [3.4:11.9]%stat (before unfolding) ds/dt : 4%syst lumin; 1%syst (acc.+eff.+backg.+tag) 0.7%syst unfold. B : 1%stat 1%syst from t 0.7%syst from unfolding ds/dt(t=0) : 0.3%stat 0.3%syst (optics) 4%syst lumin 1%syst (acc.+eff.+backg.+tag) ∫ ds/dt : 4%syst lumin 1%syst (acc.+eff.+backg.+tag) 0.8%stat extrap. • sTOT : (+0.8% -0.2%)syst 0.2%stat 2.7%syst = (+2.8%-2.7%)syst 0.2%stat • sEL : 5%syst 0.8%stat • sINEL : (+2.4%-1.8%)syst 0.8%stat TOTEM: pp Total Cross-Section B t=0 = (20.1± 0.2 (stat ) ± 0.3(syst ) ) GeV-2 Elastic exponential slope: Elastic diff. cross-section at optical point: ds el dt = (503.7 ±1.5(stat ) ± 26.7(syst ) )mb / GeV 2 t=0 Optical Theorem, 0.1400..01 08 Total Cross-Section ( s T = 98.3± 0.2 (stat) ± 2.7 (syst) éë +0.8 (syst from r ) -0.2 ùû ) mb TOTEM: pp Inelastic Cross-Section σ el 24.8 0.2 (stat) 1.2 (syst) mb ( s T = 98.3± 0.2 (stat) ± 2.7 (syst) éë +0.8 ù -0.2 û (syst from r ) Inelastic Cross-Section s inel s tot s el 73.5 0.6 (stat) mb 1.8 (syst) 1.3 sinel (CMS) = (68.0 2.0(syst) 2.4(lumi) 4.0 (extrap)) mb sinel (ATLAS) = (69.4 2.4(exp) 6.9 (extrap)) mb sinel (ALICE) = (72.7 1.1(mod) 5.1 (lumi)) mb ) mb Total, Elastic, Inelastic Cross-Section Acknowledgments • Special acknowledgments to the LHC team for their support and for the development of the 90m optics. • Special acknowledgments to CMS for their collaboration and for providing TOTEM with the luminosity measurements. PERSPECTIVES ON DIFFRACTIVE PHYSICS & CROSS-SECTIONS TOTEM Analysis Plans • Full t-range pp elastic differential cross-section • Total cross-section from elastic differential crosssection at extended lower t limit (using CMS lumi) • Total cross-section with lumi-independent method (using inelastic rate T1+T2) • SD, DPE,... t-differential cross-sections • SD, DPE,... channels: x, mass, rapidity gaps • dN/dh • Ions runs (in future pA) jointly with CMS pp Interactions Non-diffractive Diffractive Colour exchange Colourless exchange with vacuum quantum numbers dN / d Dh = exp (-Dh) dN / d Dh = const Incident hadrons acquire colour and break apart GOAL: understand the QCD nature of the diffractive exchange Incident hadrons retain their quantum numbers remaining colourless Elastic Scattering ~25 mb Single Diffraction ~10 mb M ~5 mb Double Diffraction Double Pomeron Exchange M ~1 mb << 1 mb Measure s (M,x,t) All the drawings show soft interactions. In case of hard interactions there should be jets, which fall in the same rapidity intervals. ~60 mb Diffractive scattering is a unique laboratory of confinement & QCD: A hard scale + hadrons which remain intact in the scattering process. Inelastic and Diffractive Processes (h = -ln tg q/2) Single diffraction low x Correlation between leading proton and forward detector T2 SD Rapidity Gap MX 2 = x s Dh = -ln x sector 45 RP sector 56 IP T2 T2 RP h Single diffraction large x correlation between leading proton and forward detector T2 SD Rapidity Gap MX 2 = x s Dh = -ln x h sector 45 RP sector 56 IP T2 T2 RP Double Pomeron Exchange (DPE) DPE Rapidity Gap Dh -ln x1 MPP2 = x1 x2s -ln x2 h ln tan q/2 Use the LHC as a Pomeron-Pomeron (Gluon - Gluon) Collider - GGC Double Pomeron Exchange (DPE) correlation between leading protons and forward detector T2 sector 45 RP low ξ sector 56 IP T2 T2 RP high ξ Example of DPE Mass Reconstruction x1 < 1.5%; x2 > 5.0% Low-b RP vertical RP horizontal T2 Mass [GeV] Preliminary Data Oct’11: Elastic + DPE RP 45 .AND. RP56 b 90m RP @ 4.8 s ~no pile-up Data Oct’11: Elastic + DPE Angular correlations Preliminary Data Oct’11: Elastic Differential Cross-Section Preliminary Extended low-t limit Raw distribution (to be corrected for acceptance, ...) Preliminary Data Oct’11: DPE tagging Raw distribution (to be corrected for acceptance, ...) Distribution integrated on x Preliminary Data Oct’11: DPE Cross-Section Preliminary Data Oct’11: SD Cross-Section Analysis in progress Raw distribution (to be corrected for acceptance, ...) MEASUREMENT OF dN/dh WITH T2 TELESCOPE T1+T2: towards inelastic rate measurements T1 telescope – Fully operational – Calibration, efficiency, optimisation of the reconstruction algorithms… – For the moment T1 serves as an event counter helping T2 – Soon ready for analysis 100.00 90.00 80.00 70.00 60.00 50.00 40.00 30.00 20.00 10.00 0.00 Efficiency (triple) Wire Efficiency 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 T1 Efficiency calculated with tracks reconstructed using only hits in the other 4 planes Inelastic rate analysis: BX runs of T1 and T2 • T2 trigger inefficiency in T2 acceptance range • T2 acceptance trigger inefficiency (track in T1 and not in T2) Background estimation (non-colliding BX runs) • beam-gas (checked one-sided) background in the trigger rate T2 telescope Plus Far (H1) T2 telescope Plus Near (H0) Minus Near (H2) Minus Far(H3) T2 Pythia version 8.107 TOTEM T2 : T2 4/4ers To be published dN/dh t> 0.3*10-10s At least 1 Track in 5.3 < h < 6.5 Pt > 30 MeV/c Average Ions 2011: CMS + TOTEM joint data-taking Trigger CMS >>> TOTEM Trigger Ratio Trigger Rate CMS trigger rate = 1.7/1.8kHz, T2 CC=5planes, ForkDelay f8, 356bs,I1I2=3.34e+12,L=2.6e+26 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 (PN&CMS)/CMS (PF&CMS)/CMS (MF&CMS)/CMS 0 100 From Spring 2012: Trigger 200 Gain 300 TOTEM >>> CMS 400 7 TeV dN/dh analysis @ LHC : ALICE, ATLAS, CMS, LHCb & TOTEM-T2 LHCb