Quarkonium Physics at CMS

Transcription

1 Quarkonium Physics at CMS Daniele Fasanella University & INFN of Bologna on Behalf of the CMS Collabora4on

2 CMS Quarkonium Studies Heavy quarkonia are an excellent laboratory for understanding QCD non- rela4vis4c due to their high mass nonperturba4ve effects can be simplified and constrained Defini4ve understanding s4ll a challenge, several models compe4ng for confirma4on Renewed interest in quarkonium spectroscopy since the discovery of the XYZ exo4c states: search of new possible states new measurements needed to understand their true nature CMS already studied many quarkonia with di- muons final states produc4on cross sec4on for S- wave quarkonia observa4on of χ cj states study of the X(387) exo4c Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 Resonance Mass c (S) hadrons c (1S) hadrons b (3S) b (S) b (1S) hadrons (S), 0 (3S) hadrons (S) hadrons (1S) J PC = hadrons J/ (1S) hadrons radiative hadrons h b (P) h b (1P) c0 (1P) BB threshold b0 (P) b0 (1P) hadrons c1 (1P) c (1P) hadrons J PC = b1 (P) b1 (1P) Bo5omonium Family X(387) h c (1P) b (P) b (1P) DD threshold Charmonium Family

3 Muon system informa4on matched to an inner- tracker track for improved momentum resolu4on Muons in CMS High precision p measurement rigger & Identification Inner racker: Silicon pixel and strip layers Muon System 3 types of gaseous detectors rigger choices of key importance for low energy studies Physical objects reconstructed at trigger level to select high purity signals 0 Run 011 Run Strategy Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 3

4 S- wave quarkonium states Unbinned Maximum Likelihood fit to μ + μ invariant mass distribu4ons Signals modeled with Crystal Ball func4ons Mass differences are fixed from PDG, common resolu4on value (scaled by mass) Yields then corrected for Acceptance (from MC) and Efficiency (from data- driven methods) muon acceptance is strongly dependent on produc4on polariza4on Events / ( 0.0 GeV/c ) 3 χ /n DoF = 94.4/99 ψ(s) CMS - s = 7 ev L = 37 pb data total fit background 8 < p < 9 GeV/c y < 1. Υ(1S) Υ(S) Υ(3S) µ + µ invariant mass (GeV/c ) Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 4

5 Inclusive Produc4on Eur.Phys. J C71, 1575 (011) JHEP 0, 011 (01) - inclusive µ + µ, corrected for acceptance Inclusive cross sec4on comprises 3 produc4on methods in hadron collisions: Prompt: Directly from pp collisions Feed- down from heavier states as χ c and ψ(s) Non Prompt from b- hadron decays Very low p range covered using first 314 nb - 1 of data dy (nb/) /dp σ d B 3 1 CMS Eur. Phys. J. C71 (011) < y < 1. ( 0) 1. < y < 1.6 ( ) 1.6 < y <.4 ( 1) his paper 0.0 < y < 0.9 ( 0) 0.9 < y < 1. ( 0) 1. < y < 1.6 ( ) 1.6 < y <.1 ( 1).1 < y <.4 ( 1) s = 7 ev L = 37 pb With 37 pb - 1 already covered a p range up to 70 GeV/c - Luminosity and polarization uncertainties not shown Unpolarized scenario results p Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 5

6 Non prompt Frac4on Frac4on coming from b- decay extracted with a - Dimensional fit of invariant mass and pseudo- proper decay length SV μ + l distribu4on components: prompt Resolu4on func4on non prompt Resolu4on func4on convoluted with exponen4al background Pre- fiked in mass sidebands L xy PV μ - Decay length resolu4on described by "per- event uncertainty" on l Results in agreement with ALAS, higher frac4on of from B- decays at LHC energy w.r.t. CDF Fraction of from b hadrons p [GeV/c] Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 6 ALAS.3 pb 0.00 < y < 0.75 CDF s = 1.96 ev y < 0.6 PRD 71 (005) s = 7 ev CMS 36.7 pb 0.0 < y < 0.9

7 ψ(ns) cross sec4ons JHEP 0, 011 (01) dy (nb/) /dp σ d B dy (nb/) 3 /dp σ d B prompt µ + µ, corrected for acceptance CMS Luminosity and polarization uncertainties not shown s = 7 ev L = 37 pb 0.0 < y < 0.9 ( 65) 0.9 < y < 1. ( 15) 1. < y < 1.6 ( 5) 1.6 < y <.1 ( 5).1 < y <.4 ( 1) prompt NLO NRQCD p - non-prompt µ + µ, corrected for acceptance CMS Luminosity uncertainty not shown s = 7 ev L = 37 pb 0.0 < y < 0.9 ( 65) 0.9 < y < 1. ( 15) 1. < y < 1.6 ( 5) 1.6 < y <.1 ( 5).1 < y <.4 ( 1) FONLL p dy (nb/) /dp ψ(s) σ d B dy (nb/) /dp ψ(s) σ d B Daniele Fasanella - IFAE 01 - Ferrara 13/4/ prompt ψ(s) µ µ, corrected for acceptance CMS Luminosity and polarization uncertainties not shown s = 7 ev L = 37 pb 0.0 < y < 1. ( 5) 1. < y < 1.6 ( 5) 1.6 < y <.4 ( 1) prompt NLO NRQCD ψ(s) p + - non-prompt ψ(s) µ µ, corrected for acceptance CMS Luminosity uncertainty not shown p s = 7 ev L = 37 pb 0.0 < y < 1. ( 5) 1. < y < 1.6 ( 5) 1.6 < y <.4 ( 1) FONLL ψ(s) Excellent agreement with NRQCD predic4ons PROMP NON-PROMP for, feed down effect included in theory reduced theore4cal uncertain4es for ψ (S) in absence of feed- down Comparison with FONLL predic4ons: For : agreement below 30 GeV above 30 GeV FONLL overes4mate data For ψ (S): agreement in the measurement region 7

8 ψ(s) to cross- sec4ons ra4os JHEP 0, 011 (01) Cross Sec5on Ra5o calcula5on: Systema4c uncertain4es largely cancel (Luminosity, Single Muon Efficiencies ) Direct produc4on with same polariza4on Residual polariza4on effect from coming from feed- down No y dependence seen, results as func4on of p B ψ(s) X Branching Frac5on measured fiqng the non- prompt cross- sec4on ra4o with FONLL or EvtGen curves prompt R non-prompt R CMS prompt y <.4 prompt NLO NRQCD s = 7 ev L = 37 pb Prompt Ratio CMS p s = 7 ev L = 37 pb y <.4 non prompt FONLL, scaled to data EvtGen, scaled to data Non-Prompt Ratio 0.05 In agreement with world average (4.8±.4) 3 improving rela4ve uncertainty by factor 3 main uncertain4es from other PDG BRs p Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 8

9 Β(µµ) (nb/) dy σ/dp d Lumi. uncertainty (11%) not shown Unpolarized ϒ(nS) assump4on ϒ(nS) Cross Sec4ons CMS, s = 7 ev L = 3 pb, y < pυ Υ(1S) Υ(S) Υ(3S) ϒ(1S) and ϒ(S) include feed- down from higher- mass states Results compared to D0 and CDF measurements Assuming cross sec4on uniform in rapidity an increase by a factor 3 is observed at s = 7 ev σ Β (µµ) ratio CMS, s = 7 ev L = 3 pb, y < Υ(3S) / Υ(1S) Υ(S) / Υ(1S) Phys. Rev. D 83, (011) pυ stat. syst. total Consistent shape to PYHIA both as func4on of p and y integrated cross sec4on overes4mated by a factor Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 9

10 χ cj γ mass distribution CERN- CMS- DP χ C1 Excellent resolu4on (< MeV ) for photons converted in the tracker volume χ C χ c1 and χ c (Δm ~45 MeV) peaks resolved in the γ spectrum χ C0 Studies on χ cj states discriminate between different theore4cal produc4on models evaluate the feed- down correc4ons to prompt produc4on Daniele Fasanella - IFAE 01 - Ferrara 13/4/01

11 he X(387) state Discovered in 003 by Belle its nature s4ll unclear A clear signal is established in 0 in the π + π - decay channel A pair of compa4ble good quality opposite- charged ψ(s) tracks associated to a reconstructed 4- track vertex fit with mass fixed to the PDG value Measured the quan4ty CMS- PAS- BPH X(387) in the kinema4cal region p (X) > 8 GeV and y(x) <. Acceptance and efficiency correc4on from simula4on applied on the mass spectrum yields Pythia 6 with mass of χ c1 (J PC =1 ++ ) set to 3.87 GeV Null polariza4on assumed 30% non- prompt frac4on assumed Ra4o results R = ± (stat.) ± (syst.) Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 11

12 Conclusions CMS has issued several studies on heavy quarkonia with the first LHC data: Differen4al cross- sec4ons in p and y of and ψ(s) mesons prompt and non- prompt contribu4ons separated general good compa4bility with NRQCD and FONLL predic4ons consistent results with other LHC experiments Differen4al cross- sec4ons in p for ϒ(nS) states shape compa4ble to PYHIA and results at evatron χ cj peaks resolved in their radia4ve decay to, using converted photons Measurement for the X(387) to ψ(s) cross sec4on ra4o Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 1

13 Bibliography prompt and non- prompt cross sec4ons in pp collisions at s = 7 ev, Eur.Phys. J C71, 1575 (011) and ψ(s) produc4on in pp collisions at s = 7 ev, JHEP 0, 011 (01) ϒ produc4on cross sec4on in pp collisions at s = 7 ev, Phys. Rev. D 83, (011) Observa4on of the χ c states with 1.1{ - 1, CERN- CMS- DP Measurement of the produc4on cross sec4on ra4o of X(387) and ψ(s), CMS- PAS- BPH Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 13

14 BACKUP

15 he CMS detector SOLENOID 3.8 B-field ECAL Scintillating PbWO 4 Crystals CALORIMEERS HCAL Plastic scintillator/ brass sandwich RACKER MUON BARREL MUON ENDCAPS Silicon Strips Pixels Drift ubes (D) Resistive Plate Chambers (RPC)" Cathode Strip Chambers (CSC) Resistive Plate Chambers (RPC)" 15

16 16 X(387) with 011 Data ψ(s) In 011 larger sta4s4c collected with a trigger restricted to the CMS barrel With first 896 pb - 1 N ψ(s) = 7594 ± 518 (stat) N X(387) = 5303 ± 341 (stat) X(387)

17 Acceptances p Single Muon Acceptance Acceptance Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 y Υ A ϒ(nS) Acceptance Υ y < Υ(3S) Υ(S) Υ(1S) pυ Polarized ϒ(nS) Acceptance 17

18 First CMS paper on Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 18

19 ψ(ns) Cross-section overview N fit = signal yield from fit to µµ invariant mass Ldt = integrated luminosity (4% uncertainty) A = geometrical and kinematical acceptance Strongly dependent on production polarization η µ <1. p >4 GeV/c 1.< η µ <.4 p >3.3 GeV/c ε = dimuon efficiency = ε(µ + ) ε(µ - ) ρ ε vertex single muon trigger and reconstruction ε(µ), data-driven via ag & Probe vertexing of opposite sign dimuons (Prob>1%) selection based on high quality tracks associated to muon segments: cuts on n hits, χ, d xy, d z ρ express the correlation between the two µ efficiencies o trigger settings remove too close µ (to reduce single µ faking double µ), inducing sizable correlations Offline rejection of forward muons bending towards each other Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 19

20 ψ(ns) Cross Sec4ons uncorrected for acceptance dy (nb/) /dp σ d <A> B prompt µ + µ, uncorrected for acceptance CMS Luminosity uncertainty not shown s = 7 ev L = 37 pb 0.0 < y < 0.9 ( 65) 0.9 < y < 1. ( 15) 1. < y < 1.6 ( 5) 1.6 < y <.1 ( 5).1 < y <.4 ( 1) dy (nb/) /dp ψ(s) σ d <A> B prompt ψ(s) µ µ, uncorrected for acceptance CMS Luminosity uncertainty not shown s = 7 ev L = 37 pb 0.0 < y < 1. ( 5) 1. < y < 1.6 ( 5) 1.6 < y <.4 ( 1) ψ(s) Prompt dy (nb/) /dp σ d <A> B p - non-prompt µ + µ, uncorrected for acceptance CMS s = 7 ev L = 37 pb 0.0 < y < 0.9 ( 65) 0.9 < y < 1. ( 15) 1. < y < 1.6 ( 5) 1.6 < y <.1 ( 5).1 < y <.4 ( 1) Luminosity uncertainty not shown dy (nb/) /dp ψ(s) σ d <A> B p + non-prompt ψ(s) µ - µ, uncorrected for acceptance CMS Luminosity uncertainty not shown s = 7 ev L = 37 pb 0.0 < y < 1. ( 5) 1. < y < 1.6 ( 5) 1.6 < y <.4 ( 1) ψ(s) Non- Prompt p Daniele Fasanella - IFAE 01 - Ferrara 13/4/ p 0

21 B fraction results Above p 0 GeV, more than 50% of the and ψ(s) mesons result from B decays non-prompt fraction CMS - s = 7 ev L = 37 pb ; y < 0.9 ; 0.9 < y < 1. ψ (S); y < p non-prompt fraction CMS - s = 7 ev L = 37 pb ; 1. < y < 1.6 ψ (S); 1. < y < p non-prompt fraction CMS - s = 7 ev L = 37 pb ; 1.6 < y <.1 0. ;.1 < y < ψ (S); 1.6 < y < p Daniele Fasanella - IFAE 01 - Ferrara 13/4/01 1