Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 1 Inclusive, prompt and non-prompt J/  production in pp collisions at 7 TeV Probing QCD at the LHC, Quarkonium2011, Vienna Darren Price, INDIANA UNIVERSITY on behalf of the ATLAS Collaboration

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 2 Introduction In this talk is presented measurement of the:  Inclusive J/  production cross-section  Fraction of J/  from B-decays  Non-prompt J/  production cross-section  Prompt J/  production cross-section using the ATLAS detector with ~2.2 pb -1 data from 2010 running. The measurements are presented both differentially as a function of J/  p T and rapidity, and integrated over the maximum span of these to provide integrated cross-sections Experimental uncertainties are at the 10—15% level across the range of measured cross-sections, and the results are systematics limited over the bulk of the distributions Results are compared to theoretical predictions from Colour Evaporation Model, Colour Singlet NNLO* and FONLL where appropriate. arXiv:

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 3 Dataset selection and trigger Trigger selection: Use single muon seeded trigger (and Minimum Bias Scintillator based trigger in very early data-taking) with open (~0 GeV), 4 GeV and 6 GeV thresholds as instantaneous luminosity increased (to keep rate under control) B-fraction measurement uses a logical OR of all of these triggers, giving increased candidate events and (slightly) higher integrated luminosities Event-based selection:  Has two reconstructed muons (with Inner Detector matched track).  Three tracks associated to Primary Vertex (PV)  Tracks associated to these muons/PV pass loose selection criteria of at least one pixel hit, and at least six hits in the Silicon tracker

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 4 Candidate selection Combined muon Muon spectrometer Calorimeters Inner Detector Tagged muon Muons associated to J/  candidate may be:  Combined (full Muon Spectometer & Inner Detector track measurement with fit between the two)  Tagged (Inner Detector measurement associated to at least one hit in Muon Spectrometer)  Tagged increases chance of fake muon signature, so require at least one of muons in pair to be combined  At least one muon in pair must have been the object that fired the trigger.  Muons must have p>3 GeV, p T >1 GeV, |  | 0, silicon hits>5

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 5 Event/candidate selection 2.2 pb -1  = 46 MeV  = 111 MeV

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 6 Basic strategy of inclusive cross-section analysis method is: Reconstruct J/  candidates in p T -y bins Correct candidate-by-candidate for efficiency, bin migrations, acceptances N corr =  w -1. N reco Fit resultant weighted yields to derive signal component N corr  N J/  corr Extract resultant cross-section from N J/  corr in given analysis bin Measurement of inclusive cross-section Detector acceptance Reconstruction efficiency Trigger efficiency Bin migration ID reco efficiency (per muon track)

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 7 Spin-alignment and acceptance ATLAS CMS LHCb Graphic from C. Lourenco Acceptance maps correct from offline reconstruction efficiency to total inclusive distribution Model-dependent on spin-alignment scenario Also correct for differences between prompt and non-prompt J/  spectra

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 8 Bin migration and track/vertex efficiencies Bin migration effects  Due to finite detector resolution J/  candidate measured in one bin at reconstruction level may be identified with a different analysis bin before smearing.  Correct for by parameterising unfolded cross-section, smearing with muon resolution measured in ATLAS, and looking at change in yields in given bin  Effect varies from 0.1% to 3% across measured phase space ID track reconstruction  ID track reco efficiency correction 99.5% per (muon) track with 0.5% uncertainty per track added linearly Vertex requirement  Require di-muon pair to fit to common vertex. Determined that impact on (real) J/  candidates was below 0.1% and so correction is neglected.  Requirement does reduce continuum background

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 9 Trigger efficiencies Trigger efficiency maps derived from hybrid scheme of finely- binned Monte Carlo (needed to remove biases) reweighted using Tag & Probe data from J/  (low p T ) and Z (high p T ) decays  Significant charge dependence observed (and corrected for)  Muon turn-on thresholds needed accurate handling  Fine granularity needed to properly model features (even at high p T ) Efficiencies plateau at around % dependent on pseudorapidity

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 10 Reconstruction efficiencies Reconstruction efficiency maps derived from Tag & Probe data from J/  supported by Z   derived data at higher p T for improved precision in plateau region Reconstruction efficiency for low p T from J/  decays Reconstruction efficiency at high p T from Z   data

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 11 Weighted fits and cross-section extraction For inclusive cross-section measurement, a binned  2 fit was used Was found to give stable unbiased weighted fit results w.r.t unbinned maximum likelihood fits once restricted to fine p T —y slices as in this analysis LOW P T, CENTRAL RAPIDITYHIGH P T, FORWARD RAPIDITY

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 12 Systematic studies: “acceptance” Acceptance map MC statistics: Obtained from dedicated MC simulation. Statistical uncertainties on maps bin-to-bin propagated through to final result (contribution at level of 1-2%) Bin migration effects Bin migration effects were studied, corrections applied (0.1—3%) and variation of bin migration within bin considered as systematic on correction ID track reconstruction ID track reco efficiency correction 99.5% per muon track with 0.5% uncertainty per track added linearly Kinematic dependence Variation of MC spectra to make acceptance maps, and correction for slight differences in non-prompt/prompt acceptance assigned as systematic (max 1.5%) Final state radiation Central result is corrected back to J/  kinematics rather than final state muon kinematics, systematic due to FSR is <0.1% (NB: taking effect of FSR on/off is overestimate)

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 13 Systematic studies: other components Spin alignment Spin-alignment uncertainty is maximum envelope of cross-section re-casted under different spin-alignment hypothesis Luminosity Quoted 3.4% uncertainty from Van der Meer scans Muon reconstruction efficiency Uncertainties on J/  reco. efficiency maps from data and uncertainties on MC/data scale factors propagated through to final result (5—10%) Fit uncertainty Derived via pseudo-experiments – approx. 1—3% contribution Trigger efficiency Similarly, uncertainties from data maps propagated through to final result (~5% effect) J/  vertex finding and primary vertex efficiencies Both these efficiencies retain more than 99.9% signal, no uncertainty assigned

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 14 Sources of uncertainty Sources of systematic uncertainty, and total uncertainties in each analysis bin

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 15 Inclusive cross-section results arXiv:

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 16 Integrated inclusive cross-sections We also sum up the measured differential inclusive cross-sections in two regions and quote the integrated cross-sections (taking into account correlations in the uncertainties) For p T >7 GeV, |y|<2.4 (maximum rapidity span) For p T >1 GeV, 1.5<|y|<2.0 (maximum transverse momentum span)

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 17 Measurement of non-prompt fraction Perform simultaneous unbinned maximum likelihood fit on invariant mass and pseudo-proper time distribution (used as discriminant for prompt/non- prompt J/  ) to determine fraction in p T —y bins Mass fit: signal – gaussian with per-event error background – Chebyshev polynomial Lifetime fit: signal – delta function plus exponential convoluted with gaussian with per-event error to account for resolution background – symmetric positive/negative exponentials plus positive exponential convoluted with gaussian with per-event error for resolution

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 18 Simultaneous mass/lifetime fit projections

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 19 Systematic uncertainties for B-fraction Many systematics cancel fully or partially in taking the ratio. Effects studied include:  Impact of acceptance, muon reconstruction, trigger efficiencies on fraction  Cancellation within statistical uncertainties for efficiency  Correction for non-prompt/prompt acceptance and uncertainty assigned  Background model variations  Per-event convolution function changed to per-event double Gaussian  Chebyshev polynomial of degree 2 changed to 1 and 3 to test stability  Spin alignment uncertainty of prompt/non-prompt components propagated  Multiple primary vertices: No significant variation seen  Mass region: wider mass, include/exclude  (2S): Stable; no systematic assigned  Simultaneous fit: mean invariant mass plotted as function of lifetime Found to be flat, no correlation systematic assigned

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 20 Non-prompt fraction results arXiv:

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 21 Prompt and non-prompt cross-sections From inclusive cross-section and non-prompt fraction we can derive the prompt and non-prompt cross-sections Take into account uncertainty correlations that exist between the two measurements (overlapping data samples!) and merge analysis bins where required For the prompt cross-section we compare to predictions from  NLO/NNLO* pQCD (Colour Singlet) [J.P.Lansberg]  Colour Evaporation Model [R. Vogt] For the non-prompt cross-section we compare to predictions from  Fixed Order Next-to-Leading-Log (FONLL) [M. Cacciari]

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 22 Non-prompt cross-sections Integrated cross-sections again provided in two regions: Assume isotropic distribution for spin-alignment central value (for consistency with inclusive and prompt results) Spin-alignment envelope for non-prompt covers possible variation from isotropic i = 0 to  = ~±0.1 as measured by CDF/Babar (only  * angle dependence!)

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 23 Non-prompt cross-section arXiv:

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 24 Prompt cross-sections Integrated cross-sections again provided in two regions: Assume isotropic distribution for spin-alignment central value (for consistency with inclusive and prompt results) Spin-alignment envelope here covers maximal envelope of possible variation of result due to spin-alignment configurations in both angles  * and  *

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 25 Prompt cross-section results arXiv:

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 26 Summary Measurement of inclusive cross-section of J/  in four rapidity bins from p T 1—70 GeV (span rapidity-dependent) [arXiv: ] Measurement of non-prompt production fraction and derivation of prompt and non-prompt production cross-sections from these two measurements  Highest reach in p T of any previous such measurement  Complementary results to other LHC measurements (rapidity and p T ), good agreement with CMS where measurements overlap  Non-prompt FONLL predictions do good job of describing non-prompt production within scale uncertainties  Description of prompt production more problematic, but clearly represent a step forward over historical predictions  Expect many more results from quarkonia sector from ATLAS in future!

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 27 Additional slides

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 28 Di-muon invariant mass distribution Combined + combined di-muon pair, 15,2.5 GeV

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 29 Charge-dependence of muon reco./trigger Due to the toroidal magnetic field of the ATLAS Muon Spectrometer, muons with positive (negative) charge are bent towards larger (smaller) . Introduces a charge dependence of the muon reconstruction/trigger efficiencies, particularly relevant at very large |  |, where muons of one charge may be bent outside the detector geometrical acceptance, and at low p T, where muons of one charge may be bent back before reaching spectrometer stations

Darren Price – Production of J/ at ATLAS :: Quarkonium2011, Vienna :: April 18 th ‘11 Page 30 Charge-dependence of muon reco./trigger Reconstruction efficiency of Combined (CB) + Tagged (ST) muons as a function of charge*pseudorapidity in MC and data L OW P T H IGH P T