Diffraction in ALICE - status and perspectives

Transcription

1 Diffraction in ALICE - status and perspectives Rainer Schicker Phys. Inst., Heidelberg July 20, 2015 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

2 A historical review Results from Run I Expectations for Run II Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

3 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

4 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

5 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

6 The ALICE experiment Scintillator arrays: Central Barrel η < 0.9 tracking: ITS+TPC trigger detectors: SPD, TRD, TOF Muon spectrometer -4.0 < η < -2.5 tracking trigger chambers VZERO-A: 2.8 < η < 5.1, segmented in η 0.5, φ = 45 0 VZERO-C: -3.7 < η < -1.7, segmentation as VZERO-A Zero Degree Calorimeter for detecting forward neutrons Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

7 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

8 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

9 Event topologies elast. scattering single diff. diss. double diff. diss. central prod. central prod./single diss. central prod./double diss. Identify these topologies by measuring forward scattered protons or fragments, or by detecting the rapidity gap Events defined by colour singlet exchange, Pomeron/Reggeons Rapidity gaps can also be due to photon and W ± -exchange Pomerons and photons contribute differently in pp, pa and AA Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

10 Results from Run I Analysis of double gap events in pp-collisions at s = 7 TeV with the ALICE experiment, master thesis F. Reidt, AIP Conf.Proc (2012) 17. R DG = N DG N MBand = (7.63 ± 0.02 ± 0.87) 10 4 (not corrected for detector effects) yes, rapidity gap condition is a useful concept at LHC energies Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

11 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

12 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

13 Experimental results from COMPASS A. Austregesilo SaporeGravis Workshop, dec 2-5, 2013 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

14 The power of Partial Wave Analysis A. Austregesilo, Partial Wave Analysis of COMPASS data SaporeGravis Workshop, dec 2-5, 2013 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

15 Partial Wave Analysis of ALICE central production data Partial Wave Analysis of ALICE central production data ongoing Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

16 Interest in Central Production at LHC Energies Larger cross section for higher mass states Spectroscopy of Strangeonia and Charmonia states Cross section of exclusive Strangeonia/Charmonia production? Dynamical lattice QCD calculations done for the charmonium system with resulting multiplets and supermultiplets: L. Liu et al., Excited and exotic charmonium spectroscopy from lattice QCD, JHEP 1207 (2012), known states (listed in PDG) in black M MΗc MeV 1000 Ds Ds DD non-exotic states in green exotic states in red J PC Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

17 DD The Charmonia system Search for exotic and non-exotic hybrids Hybrid states: qq-states with large admixture of a gluon component States with quantum numbers allowed in quark model are non-exotic States with quantum numbers not allowed in quark model are exotic 1500 L. Liu et al., JHEP 1207 (2012) 126. M MΗc MeV DsDs known states (listed in PDG) in black non-exotic states in green exotic states in red Many of the non-exotic states follow the n 2S+1 L J pattern as predicted by quark potential models States grouped in multiplets and supermultiplets supermultiplets of quark-antiquark pairs Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

18 The Strangeonia system Strangeonium sector not well known Strange quarkonia consist of mesons (u,d,s) with at least one strange quark in the dominant qq-component Kaonia and anti-kaonia consist of ns- and sn-configurations (n=u,d) Strangeonia is composed of the ss-configuration Up to mass of 2.2 GeV/c 2, 22 strangeonia states are expected, only 7 are known The 7 known states are η η (maximally mixed), φ(1019), h 1 (1386), f 1 (1426), f 2 (1525), φ(1680), φ 3(1854) φ(1680), φ3 (1854) are controversial T. Barnes, N. Black, P.R. Page, Strong Decays of Strange Quarkonia, Phys. Rev. D68 (2003) Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

19 New detectors for Run II Run I veto detectors VZERO Run II new detectors ADA, ADC: (in addition to VZERO) 2.8 < η < <η <6.3 7<η < < η < 1.7 Scintillation det. ADA 4.8<η <6.3 accept. diffr. masses M x Detectors ADC, ADC: extend accept. to lower masses in single/double diffractive dissociation in pp-collisions improve exclusivity condition in pp, ppb and PbPb collisions rejection of beam-gas events ADA/ADC det. taking data Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

20 Plans for Run II Run II has officially started! First stable proton beams at s = 13 TeV declared on June 3. Run II expectations: pp-collisions at s = 13 TeV ( maybe higher later in the run), fb 1 delivered to ATLAS and CMS Pb-Pb at s = 5.1 TeV, 1 nb 1 p-pb, s under discussion: 5.1 TeV (same s as in PbPb) 8 TeV ( max. s available) Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

21 Summary and outlook a wealth of Run I data available from ALICE collaboration pp collisions enhanced production of f 0(980), f 2(1270) in double gap events Partial Wave Analysis under development ppb and PbPb collisions J/ψ production in PbPb collisions at midrapidity ψ(2s) production in PbPb collisions at midrapidity ρ production in PbPb collisions at midrapidity J/ψ production in PbPb collisions at forward rapidity J/ψ production in ppb collisions at forward rapidity photon-photon collisions γγ e + e in PbPb at midrapidity new detector system ADA, ADC for improved pseudorapidity coverage in Run II Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

22 Backup slides Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

23 J/Ψ production at forward rapidity in PbPb-collisions ALICE Collaboration, Phys. Lett. B718 (2013) 1273 measurement J/ψ production at forward rapidity J/Ψ in µ + µ channel trigger: single muon trigger p T > 1 GeV/c at least one hit in VZERO-C no hits in VZERO-A not much discriminating power of models at this rapidity, models without nuclear gluon shadowing disfavored Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

24 J/ψ production at midrapidity in PbPb-collisions ALICE Collaboration, Eur. Phys. J. C73 (2013) 2617 ALICE measurement J/ψ, ψ(2s) photoproduction at midrapidity J/Ψ identified in e + e and µ + µ channels trigger: at least 2 hits in SPD number of TOF hits: 2 N TOF 6 (2 hits back-to-back) no hits in VZERO-A, VZERO-C coherent production > 60 MeV/c <p J/Ψ T incoherent production <p J/Ψ T > 500 MeV/c µ + µ inv. mass (coherent prod.) electron/muon separation based on de/dx in TPC e + e inv. mass (coherent prod.) Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

25 J/ψ production at midrapidity in PbPb-collisions Analysis J/ψ cross section coherent/incoherent cross section within rapidity y < 0.9 data sample of 23 µb 1 dσj/ψ coh = dy 0.24 (stat+sys) mb dσj/ψ inc = dy 0.17 (stat+sys) mb models without gluon shadowing inconsistent with measured cross section models with EPS09 gluon shadowing agree well with measurements Analysis γγ e + e cross section γγ e + e (m e + e > m J/ψ) analyzed within rapidity -0.9 < y < 0.9 good agreement with STARLIGHT event generator e + e -inv. mass, 3.7 < m inv < 10 GeV/c 2 Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

26 ψ(2s) production at midrapidity in PbPb-collisions Analysis ψ(2s) cross section coherent cross section within rapidity y < 0.9 data sample of 23 µb 1 identification: ψ(2s) l + l and ψ(2s) π + π l + l dσψ(2s) coh dy =0.83±0.19 (stat+sys) mb ALI PREL mass spectrum shown for ψ(2s) π + π µ + µ similar spectrum for ψ(2s) π + π e + e cross section ratio ψ(2s) / J/ψ node in ψ(2s) radial wave function, smaller ψ(2s) cross section expected GDGM-GM, STARLIGHT models underpredict ratio ψ(2s) to J/ψ Counts/30 MeV/c Pb+Pb Pb+Pb+ψ(2S) y <0.9 Coherent enriched sample p < 0.15 GeV/c T Opposite sign Like sign Signal N ψ(2s) s NN = 2.76 TeV ALICE Preliminary = 17 ± 4.1 π M µ + (GeV/c 2 ) µ π Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

27 ρ 0 production at midrapidity in PbPb-collisions ALICE Collaboration, arxiv: coherent ρ 0 photoproduction at midrapidity ρ 0 identified in π + π channel within rapidity y < 0.5 trigger low-lumi runs 2010: number of TOF hits: N TOF 2 trigger higher lumi runs: number of TOF hits: N TOF 2 at least 2 hits in SPD no hits in VZERO-A, VZERO-C pion/electron separation based on de/dx in TPC Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

28 ρ 0 production at midrapidity in PbPb-collisions π + π -mass spectrum fitted by: in blue: Söding parameterization dσ MππM dm ππ = A ρ 0 Γ(M ππ) +B 2 Mππ 2 M2 ρ 0 +im ρ 0 Γ(M ππ) A=Breit-Wigner / B=non-resonant π + π ampl. in green: BW-contr. of Söding fit in red: Ross-Stodolsky parametr. dσ dm ππ = MππM ρ 0 Γ(M ππ) A M 2 ππ M2 ρ 0 +im ρ 0 Γ(M ππ) 2 ( M ρ 0 M ππ ) k comparison to models GDL (Glauber-Donnachie- Landshoff): DL model for ρn cross sect. STARLIGHT (Nystrand): σ(ρn) = 5.0 W 0.20 γn W 1.23 γn µb excitation function for coherent and exclusive ρ 0 production Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29

29 J/Ψ production at forward rapidity in ppb-collisions ALICE Collaboration, Phys.Rev.Lett. 113 (2014) measurement of J/ψ production at forward/backward rapidity J/Ψ in µ + µ channel J/Ψ measured in p-pb 2.5 < y < 4.0, 21 < W γp < 45 GeV J/Ψ measured in Pb-p 3.6<y< 2.6, 577<Wγp < 952 GeV ALICE measurement: cross section compatible with power-law dependence up to W γp 700 GeV (x 2x10 5 ) no change of gluon PDF between HERA and LHC energy Rainer Schicker Diffraction in ALICE - status and perspectives July 20, / 29