(Experimental) Soft Diffraction at LHC Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017
Introduction selected processes: Elastic scattering p + p p + p Single diffraction p + p p + X Double diffraction p + p X + Y + σ tot, σ el, σ inel common characteristics exchange of colourless objects (Pomerons) large rapidity gaps very forward particles in final state often surviving forward proton dedicated instrumentation needed Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 2
Forward instrumentation (used in the papers discussed below) ALICE V0: η max = 3.7 (right), 5.1 (left) Forward Multiplicity Detector (FMD): η max = 3.4 (right), 5.1 (left) ATLAS Minimum-bias trigger scintillators (MBTS): η max = 3.9 ALFA: proton tagging with Roman Pots at 240 m from IP CMS Hadron Forward calorimeter (HF): η max = 5.2 CASTOR calorimeter, single side: η max = 6.6 LHCb single side, 2 < η < 4.5 TOTEM T2: η max = 4.7, T2: η max = 6.5 proton tagging with Roman Pots at 200 and 220 m from IP Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 3
Elastic Scattering : Measurement comparison dσ/dt (mb/gev 2 ) t = p 2 θ 2 : four-momentum transfer sq. 10 5 10 4 10 3 10 2 s = 13 TeV 10 1 dσ/dt (mb/gev 2 ) 10 3 s = 8 TeV 10 2 10 1 s = 7 TeV (uncertainties shown: only statistical) s = 2.76 TeV (arbitrary normalisation) TOTEM, β = 11 m, VERY PRELIMINARY! s = 7 TeV TOTEM, β = 3.5 m, EPL 95 (2011) 41001 TOTEM, β = 90 m, EPL 101 (2013) 21002 ATLAS-ALFA, Nucl. Phys. B 889 (2014) 486 10 0 10 1 10 2 PRELIMINARY s = 8 TeV s = 7 TeV PRELIMINARY PRELIMINARY 10 0 s = 8 TeV (scaled 10 ) 0.1 0.2 0.3 β = 90 m, PRELIMINARY! t (GeV 2 ) TOTEM, β = 90 m, Nucl. Phys. B 899 (2015) 527 TOTEM, β = 1000 m, Eur. Phys. J. C76 (2016) 661 ATLAS-ALFA, Phys. Lett. B 761 (2016) 158 10 3 s = 2.76 TeV s = 13 TeV (arbitrary normalisation) 10 4 TOTEM, β = 90 m, VERY PRELIMINARY! 10 5 0 0.5 1 1.5 2 2.5 3 3.5 t (GeV 2 ) different t probe different physics regimes from lowest to highest t : Coulomb interference diffractive cone: Pomeron exchange dip-bump: interference of amplitude components transition to pqcd Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 4
Elastic Scattering : Diffractive slope at low t : dσ/dt A exp( B t ) B (GeV 2 ) 21 20 19 18 17 16 15 14 13 12 11 PDG, pp PDG, pp TOTEM ATLAS-ALFA 10 1 10 2 10 3 10 4 s (GeV) up to s 3 TeV: linear in ln s; agrees with simple Regge model: dσ/dt s 2(α(t) 1), α(t) = α 0 + α t B = B 0 + 2α ln s 7 and 8 TeV measurements compatible between TOTEM and ATLAS-ALFA significantly above the linear extrapolation (dashed line) change of regime around 3 TeV? 13 TeV point available soon Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 5 0.9 TeV 2.76 TeV 7 TeV 8 TeV 13 TeV
Elastic Scattering : Dip position forward code shrinks with increasing energy: dip moves to lower t dσ/dt (mb/gev 2 ) 10 2 10 1 PRELIMINARY PRELIMINARY s = 13 TeV 10 0 s = 8 TeV PRELIMINARY 10 1 s = 7 TeV 10 2 0.2 0.3 0.4 0.5 0.6 0.7 0.8 t (GeV 2 ) (the same legend as on slide 4) Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 6
Elastic Scattering : Deviations from pure exponential dσ/dt ref deviations from the leading exponential behaviour: ref s = 7 TeV s = 8 TeV s = 13 TeV TOTEM 19.9 t, ref = 5.03 10 2 e dσ/dt ref ref 19.24 t 0.05 0 0.05 β = 90 m 0.1 0 0.1 0.2 0.3 t (GeV 2 ) 0.05 19.38 t, ref = 5.27 10 2 e dσ/dt ref ref 19.55 t 0.05 0 0.05 β = 90 m 0.1 0 0.1 0.2 0.3 t (GeV 2 ) 0.05 20.41 t, ref = 6.577 10 2 e dσ/dt ref ref 0.05 0 0.05 PRELIMINARY! β = 2500 m 0.1 0 0.1 0.2 0.3 t (GeV 2 ) ATLAS-ALFA, ref = 4.623 10 2 e 0 0.05, ref = 4.772 10 2 e 0 0.05 (stat. unc. only) dσ/dt ref ref β = 90 m 0.1 0 0.1 0.2 0.3 t (GeV 2 ) dσ/dt ref ref β = 90 m 0.1 0 0.1 0.2 0.3 t (GeV 2 ) t 0.2 GeV 2 : similar pattern at all energies and from both experiments t 0.2 GeV 2 : often rapid change of behaviour (faster decrease) Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 7
Elastic Scattering : High t TOTEM, s = 13 TeV: very preliminary, but already very strong results dσ/dt (a. u.) 10 11 10 10 10 9 10 8 10 7 10 6 10 5 10 4 10 3 10 2 elastic scattering s = 13 TeV all 10 σ fills from October 2015 O(100 %) statistics reconstruction from 220N and 220F tagging cuts at 4 σ conservative acceptance correction no other corrections 45 bot 56 top events 5.55 10 8 45 top 56 bot events 7.82 10 8 10 1 0 0.5 1 1.5 2 2.5 3 3.5 t (GeV 2 ) model predictions: 10 3 s = 13 TeV 10 2 Block et al. 10 1 Bourrely et al. 10 0 Donnachie et al. 10 1 Ferreira et al. 10 2 Godizov 10 3 Islam et al. (LxG) 10 4 Jenkovszky et al. 10 5 Petrov et al. (3P) 10 6 10 7 0 1 2 3 4 t (GeV 2 ) dσ/dt (mb/gev 2 ) oscillations in almost each model high- t : no structures! rules out many models rules out physics mechanism: optical models physics interpretation: transition between diffraction and pqcd? e.g. Donnachie-Landshoff Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 8
Elastic Scattering : Coulomb-nuclear interference at t O(10 4 GeV 2 ): interference between Coulomb and hadronic amplitude Coulomb phase known (QED) sensitivity to phase of hadronic amp. A N parameter ρ = RA N /IA N t=0 via dispersion relations: prediction of dσ tot (s)/ds sensitivity to presence of Odderon ATLAS-ALFA: 8 TeV results expected soon, method demonstrated in PhD thesis by S. H. Stark (http://cds.cern.ch/record/2283206) 0.25 0.2 0.15 0.1 0.05 0 0.05 PDG: pp pp TOTEM: s = 7 TeV, indirect, EPL, 101 (2013) 21004 s = 8 TeV, CNI, Eur. Phys. J. C76 (2016) 661 s = 13 TeV, expected uncertainty COMPETE model RRP nf L2 u (highest rank): pp pp 0.1 0.9 TeV 7 TeV 8 TeV 13 TeV 0.15 0.2 10 1 10 2 10 3 10 4 s (GeV) Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 9
Elastic Scattering : Odderon search Odderon = crossing-odd partner of Pomeron; 3 gluon JPC = 1 state studied within Regge theory (Lukaszuk, Nicolescu), QCD (Vacca, Braun, Dosch), lattice calculations (Luscher, Morningstar), BFKL-like (Bartels) at LHC, other signatures of Odderon (currently) not accessible spin dependence differences in pp and p p scattering (e.g. dip) LHC would need to decelerate protons to e.g. UA4 energy effects at large t : preliminary β = 90 m data suggest domination by a pqcd-like contribution effect of Odderon on ρ (e.g. Nicolescu, Gauron) prediction for pp: faster decrease of ρ with s expected effect ρ 0.04 TOTEM: analysis advanced, expected uncertainty σ( ρ) 0.01 chance for significant sensitivity ATLAS-ALFA: a priory similar sensitivity Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 10
Total, inelastic and elastic cross-sections σ el (green), σ inel (blue) and σtot (red) (mb) 140 130 120 110 100 90 80 70 60 50 40 30 20 10 pp (PDG) pp (PDG) Auger (+ Glauber) ALICE ATLAS, ATLAS-ALFA CMS LHCb TOTEM best COMPETE σ tot fits 11.7 1.59 ln s + 0.134 ln 2 s (list of references in backup) σ tot σ inel σ el 0.9 TeV 0 10 1 10 2 10 3 10 4 10 5 s (GeV) new results soon at 13 TeV from TOTEM (and ATLAS-ALFA) measurements at 0.9 TeV foreseen for 2018 s-dependence: in general compatible with ln 2 s at high energies Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 11 2.76 TeV 7 TeV 8 TeV 13 TeV
10 4 s (GeV) Total cross-sections : Details σtot (red) (mb) 130 120 110 100 pp (PDG) pp (PDG) Auger (+ Glauber) ATLAS-ALFA TOTEM best COMPETE σ tot fits determined via Optical Theorem: σ tot IA el (t = 0) 90 7 TeV 8 TeV 13 TeV 80 TOTEM vs. ATLAS-ALFA 7 TeV: compatible 8 TeV: discrepancy 2 σ elastic slopes similar (see slide 5) difference comes from normalisation (luminosity) quite different extrapolation from 7 and 8 to 13 TeV ( σ tot 10 mb) 13 TeV measurement available soon Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 12
10 4 s (GeV) Inelastic cross-sections : Details σ inel (blue) (mb) 80 pp (PDG) pp (PDG) ALICE ATLAS, ATLAS-ALFA CMS LHCb TOTEM 70 60 2.76 TeV 7 TeV 8 TeV 13 TeV observation: variety of results often: ALICE and TOTEM on the line, others (significantly) below different methods different systematics (see next slide) Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 13
Inelastic cross-sections : Determination methods ALICE, ATLAS, CMS and LHCb count minimum-bias events + experimental corrections using MC: correct for invisible cross-section (very forward) sizeable model dependent e.g. CMS: democratic over several MC e.g. ATLAS: MCs selected and tuned [CMS-PAS-FSQ-15-005] with data ATLAS-ALFA, TOTEM (+CMS): from elastic rate and luminosity dσ el /dt = 1/L dn el /dt σ el σ tot IA el (t = 0), σ inel = σ tot σ el TOTEM: luminosity independent using inelastic rate from T2 correction of N inel for very forward diffraction: not as large as for others σ tot dn el/dt(t=0) N el +N inel TOTEM at 7 TeV: 3 methods used, all results consistent confidence Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 14
Single diffraction : Overview ALICE, s = 2.76, 7 and 8 TeV [EPJ C73 (2013) 2456] count single-sided events proton not tagged, only integrated cross-section CMS: s = 7 TeV [arxiv:1503.08689, CMS-PAS-FSQ-12-005] events with rapidity gap on one side (detector edge to η = 1) proton not tagged proton t not determined cross-section as function of ξ r p ξ = p p beam TOTEM, s = 7 TeV, preliminary events with proton tag and rapidity gap 3 (4) bins of ξ cross-section as function of proton t TOTEM + CMS, s = 8 TeV, in development inelastic event classification: ND, SD, DD y ln ξ M 2 X = ξ s Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 15 X z
Single diffraction : CMS Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 16
Single diffraction : TOTEM Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 17
Single diffraction : Integral cross-section original plot from [arxiv:1503.08689], ALICE data [EPJ C73 (2013) 2456] 0.9 TeV 2.76 TeV 7 TeV 8 TeV 13 TeV green: compilation from TOTEM data, s = 7 TeV, ξ 0.022 previous slide, 3.4 < M X < 1100 GeV: (6.5 ± 1.3) mb [EPL 101 (2013) 21003], M X < 3.4 GeV (SD dominated): (2.62 ± 2.17) mb σ SD (9.1 ± 2.9) mb Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 18
Double diffraction : Overview ALICE, s = 2.76, 7 and 8 TeV [EPJ C73 (2013) 2456] count events with central rapidity gap η > 3 only integrated cross-section CMS: s = 7 TeV [arxiv:1503.08689, CMS-PAS-FSQ-12-005] events with central rapidity gap η > 3 cross-section as function of central rapidity gap η TOTEM, s = 7 TeV, [PRL 111 (2013) 262001] narrow fiducial region where background reasonable (3.4 < M X/Y < 8 GeV) no attempt made to extrapolate to full phase space TOTEM + CMS, s = 8 TeV, in development inelastic event classification: ND, SD, DD Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 19
Double diffraction : Integral cross-section 0.9 TeV 2.76 TeV 7 TeV 8 TeV 13 TeV Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 20
Summary elastic scattering measurements by ATLAS-ALFA and TOTEM s-dependence of forward slope: acceleration at s 3 TeV? non-exponentiality at low t : similar at different energies and from both experiments Coulomb-nuclear interference at very low t : sensitivity to Odderon contribution total, elastic and inelastic cross-section measurements by ALICE, ATLAS, CMS, LHCb and TOTEM s-dependence generally compatible with ln 2 s growth non-negligible differences in σ inel can be related to MC corrections single diffraction differential measurements by CMS (ξ) and TOTEM (t) integral measurements by ALICE, CMS and TOTEM double diffraction differential measurement ( η) by CMS integral measurements by ALICE, CMS (and TOTEM in limited ph. space) Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 21
Backup Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 22
Total, inelastic and elastic cross-sections : References PDG data: K. Nakamura et al. (Particle Data Group), J. Phys. G 37, 075021 (2010) Auger: P. Abreu et al. (Pierre Auger Collaboration), Phys. Rev. Lett. 109, 062002 (2012) ALICE: Eur. Phys. J. C73 no. 6, (2013) 2456 ATLAS 7 TeV: Nature Commun. 2 (2011) 463 13 TeV: Phys. Rev. Lett. 117, 182002 ATLAS-ALFA 7 TeV: Nucl. Phys. B889 (2014) 486 548 8 TeV: Phys. Lett. B 761 (2016) 158-178 CMS 7 TeV: CMS-PAS-FWD-11-001 13 TeV: CMS-PAS-FSQ-15-005 LHCb 7 TeV: JHEP 02 (2015) 129 TOTEM 2.76 TeV: publication in preparation 7 TeV: Europhys. Lett. 101 (2013) 21004 8 TeV: Phys. Rev. Lett. 111 no. 1, (2013) 012001 Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 23
TOTEM Elastic scattering : Coulomb interference 8 TeV data with β = 1000 m optics RPs very close to the beam: 3 σ beam t min 6 10 4 GeV 2 dσ/dt (mb/gev 2 ) 10 3 A data fit at s = 8 TeV TOTEM data Coulomb standalone hadronic standalone Coulomb and hadronic combined Coulomb-hadronic interference 0 0.005 0.01 0.015 0.02 t (GeV 2 ) Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 24
TOTEM Inelastic and total cross-section inelastic cross-section: event counting with T2 (and T1) 95 % of inelastic events have at least 1 track in the T2 region only one significant MC correction: contribution from low mass diffraction 3 methods to determine total cross-section elastic observables only: σtot 2 = 16π 1 dn el 1 + ϱ 2 L dt 0 σ tot ϱ-independent: σ tot = 1 L (N el + N inel ) luminosity-independent: σ tot = 16π 1 + ϱ 2 dn el /dt 0 N el + N inel Jan Kašpar ISMD2017, Tlaxcala, Mexico 15 September, 2017 25