TOTEM results on total elastic inelastic and diffractive

TOTEM results on total, elastic, inelastic and diffractive scattering Heimo Saarikko University of Helsinki & HIP LHCP 2015 St. Petersburg - September 4, 2015 1

Overview • TOTEM detector setup @ IP 5 of LHC • Elastic p-p scattering • Inelastic and total p-p cross-sections • Measurement in Coulomb (interference) region • Diffractive cross-sections • Summary 2

Experimental Setup at IP 5 [Ref. : JINST 3 (2008) S 08007] Inelastic Telescopes: charged particles in inelastic events: multiplicities, rapidity gaps T 1: 3. 1 < | | < 4. 7 , p. T > 100 Me. V T 2: 5. 3 < | | < 6. 5 , p. T > 40 Me. V Inelastic Trigger HF (CMS) IP 5 ~ 10 m ~ 14 m T 1 CASTOR (CMS) T 2 Roman Pots: elastic & diffractive protons close to outgoing beams Proton Trigger IP 5 p. 3 Mario Deile – RP 220 3

Experimental Setup at IP 5 Inelastic telescopes: rapidity gaps T 1 T 2 IP 5 ~ 10 m ~ 14 m T 1 HF (CMS) Roman Pots: diffractive protons (di-proton Si-det stack Horizontal Pot T 2 CASTOR trigger) (CMS) Vertical Pots BPM IP 5 RP 147 RP unit RP 220 4

TOTEM Physics at LHC TOTEM TOTEM TOTEM Elastic and diffractive scattering: Pomeron exchange 5

Elastic pp Scattering: selection&data sets Selected based on topology, low | |, collinearity, & vertex Key issues: RP alignment & optics Data sets at different conditions to measure elastics over wide t-range including very low |t| � * = 1 km, 3 , 8 Te. V * = 90 m, 10 , 7 Te. V 8 M * = 90 m, 5 , 7 Te. V * = 90 m, 6 -9 , 8 Te. V * = 3. 5 m, 7 Te. V * = 3. 5 m, 18 , 7 Te. V * = 11 m, 5 -13 , 2. 76 Te. V Show results from data sets indicated by arrows 6

TOTEM d�el/d|t| Measurement @ 7 Te. V None of theoretical models really fit the data |t|dip= 0. 53 Ge. V 2 ~ |t| 7. 8 TOTEM 7 Te. V: A = 506 23. 0 syst 0. 9 stat mb/Ge. V 2 B = 19. 89 0. 27 syst 0. 03 stat Ge. V-2 (fit range: 5 10 3 < |t| < 0. 2 Ge. V 2) TOTEM 8 Te. V: B = 19. 90 ± 0. 30 Ge. V 2 (fit range: 1 10 2 < |t| < 0. 2 Ge. V 2) ATLAS 7 Te. V: B = 19. 73 0. 26 syst 0. 14 stat Ge. V-2 EPL 95 (2011) 41001 (fit range: 0. 01 < |t| < 0. 1 Ge. V 2) EPL 96 (2011) 21002 EPL 101 (2013) 21002 7 Te. V el = 25. 4 ± 1. 0 lumi ± 0. 3 syst ± 0. 03 stat mb (L from CMS with 4% unc. ) el = 24. 8 ± 1. 0 lumi ± 0. 7 syst ± 0. 2 stat mb (L independent) 8 Te. V el = 27. 1 ± 1. 2 syst+stat mb ATLAS result: 7 Te. V el = 24. 00 ± 0. 57 syst ± 0. 19 stat mb TOTEM results: (L with 2. 3% uncertainty) (91% directly measured) (67% directly measured) (90% directly measured) 7

Direct �inel Measurement ● Count events with charged particles in T 1 & T 2 ( 95 % of inelastic). ● Trigger: at least one track in T 2. x/s. SD ds. SD/dx MX > 3. 4 Ge. V/c 2 (TOTEM) Impact of Low-Mass diffraction: ● ● Extrapolation to low MX region: main source of systematic uncertainty on inel Minimal MX depends on maximal | | coverage: lower MX reachable minimal model dependence on corrections for low mass diffraction S. Ostapchenko ar. Xiv: 1103. 5684 v 2 [hepph] QGSJET-II-4 SIBYLL / PYTHIA 8 low mass contribution TOTEM (T 1+T 2: 3. 1 < | | < 6. 5) gives an unique forward charged particle coverage @ LHC direct measurement of inel with lower sys. unc. Low mass diffraction @ Mdiff < 3. 4 -3. 6 Ge. V (tuned QGSJETII-03 to observed 1 hemi fraction) inelastic Direct @ 7 Te. V 73. 7 3. 4 mb MX > 15. 7 Ge. V/c 2 (ATLAS, CMS) @ 8 Te. V EPL 101 (2013) 21003 Indirect L independent 73. 15 1. 26 mb EPL 101 (2013) 21002 72. 9 1. 5 mb EPL 101 (2013) 21004 74. 7 1. 7 mb PRL 111 (2013) 012001 8

Low-Mass Diffraction: Constraint from Nel Constraint on low mass diffraction cross-section from TOTEM data: Use total cross-section determined from elastic observables (via the Optical Theorem) no assumption on low mass diffraction inel = tot – el = 73. 2 1. 3 mb and the measured “visible” inelastic cross-section for | | < 6. 5 (T 1, T 2) inel, | | < 6. 5 = 70. 5 2. 9 mb to obtain the low-mass diffractive cross-section (| | > 6. 5 or MX < 3. 4 Ge. V/c 2 inel, | | > 6. 5 = inel - inel, | | < 6. 5 = 2. 6 2. 2 mb (or < 6. 3 mb @ 95% CL) [MC: 3. 1 1. 5 mb] 9

Total Cross Section Measurements @ 7 Te. V 1) Elastic Scatt. + Inelastic Scatt. + L (no dependence on ρ) tot = el + inel 2) Elastic Scatt. + L + Optical Th. (no assumption on low mass diffr. ) inel = tot - el 3) Elastic Scatt. + Inel. Scatt. + Optical Th. (no dependence on L ) el and inel : from tot and Nel /Ninel Method �tot (mb) �inel (mb) �el (mb) Reference 25. 4 � 1. 1 EPL 101 (2013), 21002 EPL 101 (2013), 21003 1 99. 1 � 4. 3 2 98. 3 � 2. 8 73. 5 � 1. 6 24. 8 � 1. 2 EPL 96 (2011), 21002 2 98. 6 � 2. 2 73. 2 � 1. 3 25. 4 � 1. 1 EPL 101(2013), 21002 3 98. 0 � 2. 5 72. 9 � 1. 5 25. 1 � 1. 1 2 95. 35� 1. 36 71. 3 � 0. 9 24. 0 � 0. 6 EPL 101 (2013), 21004 ATLAS / Nucl. Phys. B 889 (2014) 73. 7 � 3. 4 ρ = 0. 140 0. 007 (from Compete) Proper tracking acceptance in very forward region required: elastically scattered p detection mandatory 10

TOTEM �tot Measurement @ 8 Te. V & Summary Analysis in progress at s = 2. 76 Te. V tot from L –independent Method 7 & 8 Te. V TOTEM @ 8 Te. V PRL 111 (2013) 012001 11

d�el/d|t| Measurement @ 8 Te. V with High Statistics High statistic data sample allows a precise d el/d|t| measurement (for 0. 027 < |t| < 0. 2 Ge. V 2) “Purely” exponential slope excluded with a significance > 7 Plotting relative deviation from exponential and fitting ds/dt = A e-B(t) |t| , ( d el/d|t| = Ae-B(t|)t|) with B(t) = b 1 (Nb = 1) or B(t) = b 1 + b 2 t (Nb = 2) or B(t) = b 1 + b 2 t + b 3 t 2 (Nb = 3) TOTEM New! Nucl. Phys. B 899 (2015) 527 No = 1: B = b 1 (Reference) Nb = 2: B = b 1 + b 2 t Nb = 3: B = b 1 + b 2 t + b 3 t 2 Ø Quadratic and cubic polynomials in the exponent well describe data Ø Using the new parametrisations for extrapolation to t = 0 and applying the optical theorem, new results for tot are found in agreement with previous measurement: Nb = 2 (quadratic polynomial) Nb = 3 (cubic polynomial) tot = 101. 5 2. 1 mb tot = 101. 9 2. 1 mb 12

Elastic Scattering in the Coulomb-Nuclear Interference (CNI) Region � * = 1 km, 3� M ary TE in TO elim Pr Measurement of r by studying the CNI down to |t| ~ 6 10 -4 Ge. V 2 Reached @ s = 8 Te. V, with b* = 1000 m and RP approaching the beam centre @ ~ 3 13

Analysis of CNI Region d�/dt �|FC+H|2 = Coulomb + “interference” + hadronic - Interference formulae: + Simplified West-Yennie (SWY) [1]: past “standard”, only compatible with pure exponential hadronic amplitude with constant phase + Kundrát-Lokajícek (KL) [2]: no limitations on hadronic amplitude - phase of FH: central or peripheral �b = impact parameter of elastic pp collisions ��Re FH/ Im FH�t=0 = 1 / tan(�� t=0) modulus constrained by measurement e�B(t) = b 1 t + b 2 t 2 + … Nb = # parameters in exp. P(b) from QED P(b) �(phase of FH) accessible via interference with FC (known)! ”Central” ”Peripheral”: b (fm) Best fit method retained: 2 -stage fit: Fit 1: only b*=1 km data (very low |t|): all parameters free determines r [1] G. B. West and D. R. Jennie, Phys. Rev. 172 (1968)1413. [2] V. Kundrát and M. Lokajıcek, Z. Phys. C 63 (1994) 619. Fit 2: combined b*=1 km and 90 m data with fixed r Results coming soon 14

Soft Single Diffraction @ 7 Te. V d /dt ~ A·e-Bt mb/Ge. V 2 Low mass Mdiff = 3. 4 - 8 Ge. V T 2 T 1 CMST 1 T 2 SD, low Mdiff 1. 8 mb Mdiff = 8 - 350 Ge. V CMST 1 T 2 SD, medium Mdiff 3. 3 mb B = 8. 5 Ge. V- 2 Mdiff = 0. 35 - 1. 1 Te. V T 2 T 1 CMST 1 T 2 mb/Ge. V 2 TO High mass TE M Pre T 2 T 1 lim mb/Ge. V 2 Medium mass ina ry B = 10. 1 Ge. V- 2 Corrections included: - Trigger efficiency - Proton acceptance & reconstruction efficiency - Background subtraction - Extrapolation to t = 0 Missing corrections: Class migration � resolution & beam divergence effects Estimated uncertainties: B ~ 15% ; �~ 20% TOTEM preliminary: SD, high Mdiff 1. 4 mb B = 6. 8 SD = 6. 5 ± 1. 3 mb 3. 4 Ge. V < Mdiff < 1. 1 Te. V Ge. V- 2 Analysis of very high mass SD events ongoing 15

Soft Double Diffraction @ 7 Te. V • Both protons break up � 2 diffractive masses Mdiff 1, Mdiff 2 • Central rapidity gap |h|min, 2 |h|min, 1 For large masses ( small central gap) not easy to separate from ND events Select: sub-range with particles in both T 2 hemispheres, veto on both T 1 (“ 0 T 1+2 T 2”) 4. 7 < | |min, 1/2 < 6. 5 or 3. 4 Ge. V < Mdiff 1/2 < 8 Ge. V = 4. 7 T 1 T 2 IP = 6. 5 Event selection with high DD purity (� 70 %) 116� 25 �b SD & DD results combined seems to indicate factorisation breaking since � |� 6. 5) >> DD (4. 7 � min| � � 4. 7 �� � 6. 5) / � SD (� min � SD (4. 7 � min � elastic PRL 111 (2013) 262001 16

Summary and Outlook q Extensive programme of �tot, �el, �inel and diffractive scattering measurements @ LHC in Run I q @ �s = 7 Te. V collision data taken in special runs with different beam conditions (�* = 3. 5 m, 90 m) allowed measurements of: - elastic scattering in a wide |t| range (5· 10 -3 < |t| < 3. 5 Ge. V 2) - elastic, inelastic and total p-p cross-section (very good agreement among results from different experiments) - soft single and double diffraction q @ �s = 8 Te. V collision data taken in special runs with different beam conditions (�* = 90 m, 1000 m) and high statistics gave measurements of: - elastic scattering down to very low |t| (6· 10 -4 < |t| < 0. 2 Ge. V 2) �evidence for non-exponential slope �study of Coulomb-Nuclear interference feasible, more to come soon … - elastic, inelastic and total p-p cross-section (L-independent only) q Looking forward for new data during LHC Run II, so to perform new measurements at higher �s. . 17