Hadronic Charm: Introduction & D0Kp Andrea Dainese (INFN LNL) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Analysis Scheme Event reconstruction (RAW  ESD  AOD) Charm “production” (ESD/AOD  AOD for D’s) D0 signal selection (using PID and geom/kinem cuts) Invariant mass analysis and significance maximization (in bins of pt, y, f  FRP…) Correction for efficiencies, acceptance, BR Cross section normalisation Physics (& comp. with theory) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Heavy-quark production at the LHC Baseline predictions: NLO (MNR code) in pp + binary scaling (shadowing included for PDFs in the Pb) ALICE baseline (PPR) for charm / beauty: system : sNN : Pb-Pb (0-5% centr.) 5.5 TeV p-Pb (min. bias) 8.8 TeV pp 14 TeV 4.3 / 0.2 7.2 / 0.3 11.2 / 0.5 115 / 4.6 0.8 / 0.03 0.16 / 0.007 0.65 / 0.80 0.84 / 0.90 -- Theoretical uncertainty of a factor 2-3 MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

MC Sample for Tools Development 5×106 pp events at 14 TeV (PYTHIA “PhysicsRun” cocktail): 85% pp min. bias w/o heavy quarks ~14% pp (MSEL=1) with charm, pthard-binned ~1% pp (MSEL=1) with beauty, pthard-binned Fast production: full ITS, TPC param, no TOF, no TRD Generated via LCG in Legnaro, Torino, CNAF in April06 Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Analysis Scheme Event reconstruction (RAW  ESD  AOD) Charm “production” (ESD/AOD  AOD for D’s) D0 signal selection (using PID and geom/kinem cuts) Invariant mass analysis and significance maximization (in bins of pt, y, f  FRP…) Correction for efficiencies, acceptance, BR Cross section normalisation Physics (& comp. with theory) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Event reconstruction (RAW  ESD  AOD) Reconstruction in the barrel  tracks Standard AOD (Analysis Object Data), extracted from ESD (Event Summary Data): Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

The key issue for HF reco: track impact parameter Primary Vertex B e X d0 rec. track Distance of closest approach to the primary vertex At “high” pt: d0  ct  HF decay tracks displaced by ~100 mm  ALICE ITS with SPD < 60 mm (rf) for pT > 1 GeV/c BA, CT, LNL, PD Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Track impact parameter measurement in pp collisions Track impact parameter resolution: sd0 = svtx  strack Vertex reconstructed from tracks (LNL, To) Bias (underestimate of d0) if the considered track is used for vertex fit: s of d0 distribution for primaries s [mm] bias! bias! s of d0/error(d0) distr. for primaries 90% of tracks from D decay used to find primary vertex  primary vertex has to be reconstructed for each D candidate excluding its daughters D-decay Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Effect of ITS misalignment on d0 resolution Impact parameter resol: strack = ascatter/pt  bmeas  cmisalign Effect studied with full simulation of exptected initial (full+) and residual (after realignment) misalignments See talk tomorrow Effect on D0 measurement studied (see later) null residual full full+ Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Analysis Scheme Event reconstruction (RAW  ESD  AOD) Charm “production” (ESD/AOD  AOD for D’s) D0 signal selection (using PID and geom/kinem cuts) Invariant mass analysis and significance maximization (in bins of pt, y, f  FRP…) Correction for efficiencies, acceptance, BR Cross section normalisation Physics (& comp. with theory) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Analysis scheme (ESD/AOD ➔ AOD) Standard AOD ESD or Standard AOD + HF vertices (15-20% in size) 2-prong HF 3-prong HF ... Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

AliAnalysisVertexingHF Bari, Legnaro, Torino single-track cuts on quality, pt (d0?) [common cuts for all analyses] build all (+,-) pairs and compute secondary vtx for D+,Ds+,Lc+,D*+ for D0Kp, J/y (from B)ee loop on all tracks (+ & -): build triplets, create AliAODRecoDecayHF3Prong, apply reco cuts (common for the 3 particles?) create AliAODRecoDecayHF2Prong apply reco cuts tight D0 mass cut loop on all tracks for D*+ candidates for D0Kppp loop on all tracks (+ & -) … create AliAODRecoDecayHF … store J/y store D0 store D*+ store D+, Ds+, Lc store D0 Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Secondary vertex reconstruction Two different vertexers available classical vertexer (used also for primary vertex reco): finder + fast fitting algorithm (LNL-To) Kalman-filter vertexer, with possibility to apply topological & mass constraints (GSI), under test Possibility to remove D0 decay tracks from primary vertex  unbiased (or less biased) estimate of impact parameters x pull resolution [mm] Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Set of classes for storage and analysis of candidates AliVParticle AliAODRecoDecay PWG2 PWG3 AliAODRecoDecayHF AliAODv0 AliAODRecoDecayHF2Prong AliAODRecoDecayHF3Prong D0,J/y from B,... D+,Ds,Lc,... AliAODRecoDecayHF4Prong D0 Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Analysis Scheme Event reconstruction (RAW  ESD  AOD) Charm “production” (ESD/AOD  AOD for D’s) D0 signal selection (using PID and geom/kinem cuts) Invariant mass analysis and significance maximization (in bins of pt, y, f  FRP…) Correction for efficiencies, acceptance, BR Cross section normalisation Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Selection Variables & PID DCA: distance of closest approach between the two tracks cosq*: cosine of decay angle d0xd0: product of the two tracks rf impact parameters cosqpointing: cosine of pointing angle 3 PID “modes” considered (TOF): keep all pairs (no PID) keep only pairs with a K reject only (p,p), (K,K) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Extraction of signal raw yield: Invariant mass analysis Here, 5 million pp events (1/200 of 1-year’s statistics) pt > 0 “PPR cuts” Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Extraction of signal raw yield: Invariant mass analysis RS/TS~0.30 RS/TS~0.25 RS/TS~0.20 RS/TS~0.15 PID: (p,p), (K,K) rejected Beware of reflections: no PID Reflections Combinatorial Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Extraction of signal raw yield: Invariant mass analysis Two possible approaches: direct fit w/o bkg subtraction (only if large S/B, > 50%?) background subtraction with event mixing + fit Direct fit tried: exponential + gaussian fit side-bands with expo: initial expo parameters fit everything with expo + gauss with constraint on total integral ------------ From Fit ---------------------- Total S integral (+- 3s) = 39.7 +- 9.3 S/B (+- 3s) = 85% SGNC as S/sS (+- 3s) = 4.3 (58 for 109 evts) SGNC as S/S+B (+- 3s) = 4.3 ---------- From Simulation ------------ Total S integral (+- 3s) = 39.5 S/B (+- 3s) = 90% SGNC as S/S+B (+- 3s) = 4.3 (59 for 109 evts) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Significance maximization Optimize cut values in pt bins: maximize significance in cut-variables space (e.g. 4D space) Example: 3<pt<5 GeV/c 0<pt<1 GeV/c 2<pt<3 GeV/c 5<pt<8 GeV/c A.Rossi Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Results pp (109 evts) pp (109 evts) PPR Checked performance w/o PID: not much worsening, but have to tighten cuts (larger systematic errors?) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Analysis Scheme Event reconstruction (RAW  ESD  AOD) Charm “production” (ESD/AOD  AOD for D’s) D0 signal selection (using PID and geom/kinem cuts) Invariant mass analysis and significance maximization (in bins of pt, y, f  FRP…) Correction for efficiencies, acceptance, BR Cross section normalisation Physics (& comp. with theory) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Corrections & Errors: Beauty feed-down (~10%) Methods: Monte Carlo with state-of-the-art pQCD input use measurements from ALICE (from single m, then e) Systematic error: uncertainty on b-bbar cross section from theory (1) or data (2). For (1), the syst. error estimated to be ~8-10% according NLO pQCD Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Corrections & Errors: Acceptance, Reco & Selection Efficiency Method: Embedding of MC signal in real events, and calculate all corrections in one go (selected  in-acceptance). Average correction in {pt, y} grid use ALICE common correction framework (A.Mastroserio) Needed tuned MC (good descr. of tracking effs and resols). d0 resol. is crucial, must be evaluated from data vs pt, q, PID, NITSclusters Systematic error: - compare weights in different runs, and with the two field orientations (+z and -z) - check stability of extracted yield VS variation of cuts - repeat weights calculations (MC) with different sets for alignment corrections Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Effect of misalignment on S/B and significance (S/S+B) Residual misalignment: negligible effect “Full” misalignment: 15-20% worsening of statistical errors Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Evaluation of d0 res. from data Evaluation of d0 resolution: d0 distribution is dominated by primary particles for |d0|<d0MAX Fit in this range provides the resolution, to be then compared with that in AliRoot Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Evaluation of d0 res. from data pt  0.4 GeV/c pt  1.1 GeV/c pt  4.5 GeV/c primaries all A.Rossi Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Evaluation of d0 res. from data Fit of all tracks’ d0 distr. in the range ~ (-3s, +3s) allows to extract the d0 resolution Resolution is a convolution of track position resolution, primary vertex resolution, misalignment effects  devise method to separate track and vertex contributions Study other (complementary) methods e.g. using cosmic muons crossing all ITS  d0 resolution at high pt no misal. ITS sd0=12mm: OK! Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Analysis Scheme Event reconstruction (RAW  ESD  AOD) Charm “production” (ESD/AOD  AOD for D’s) D0 signal selection (using PID and geom/kinem cuts) Invariant mass analysis and significance maximization (in bins of pt, y, f  FRP…) Correction for efficiencies, acceptance, BR Cross section normalisation Physics (& comp. with theory) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Calibrating the probe (pp, s = 14 TeV) measured at 14 TeV, then scaled by pQCD to 5.5 TeV Expected sensitivity in comparison to pQCD: D0  Kp stat. err. vs # events ~1 month Detector configuration: ITS + TPC + TOF 1 year at nominal luminosity (109 pp events) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Charm E Loss : RAA 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) E loss calc.: Armesto, Dainese, Salgado, Wiedemann Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Heavy-to-light ratios probes colour-charge dep. of QCD energy loss probes mass dep. of QCD energy loss E loss calc.: Armesto, Dainese, Salgado, Wiedemann 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Summary Prepared software tools for reconstruction of (most) hadronic charm decays (+J/y) in one go (Ba - LNL/Pd - To) will (soon) run on ESD and on AOD will (soon) allow to choose between two vertexers to be tested on the Grid Track impact parameter measurement is crucial for hadronic charm (esp. in Pb-Pb) studied possible systematics on this quantity (primary vtx, misalignment...) D0Kp: run a realistic analysis (sgn+bkg together) on 5M pp events tried a first version of invariant mass fit to extract raw yield warning: signal reflection developed multi-dimensional SGNC maximization method results (signal SGNC) compatible with PPR ones set up procedure to apply corrections Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

EXTRA SLIDES Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

First pp data: machine scenario b* ~ 10 m (will be 0.5 m for Pb-Pb) Bunch spread: transverse sbunch (b*) ~ 70 mm, long. sbunch ~ 7.5 cm Vertex spread: transverse svertex =sbunch/2~50 mm, long. svertex = 5.3 cm Luminosity: (1/s2vertex) ~1030 cm-2s-1 (70 kHz for spp = 70 mb) Revol’s scenario: 20x10h ~5-10x107 min. bias events Subsystems directly used for D0 analysis: ITS, TPC, TOF Assumption: TPC, full ITS, half TOF (-0.9<h<0.9, Df=p ?) First pp data: detector scenario Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Candidate cuts (1) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Corrections & Errors: Acceptance, Reco & Selection Efficiency Selection efficiency: from selected to reconstructed signal Reconstruction eff.: from reconstructed to in-acceptance Acceptance: from in-acceptance to dN/dy at y=0 central Pb-Pb central Pb-Pb Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Beauty feed-down Feed-down can be up to 15% after selection Can use upper cut on |d0| to control it To subtract it: use simulation with state-of-the-art pQCD c and b predictions for LHC later, use b cross section measured at LHC later, use d0 of D0 to estimate feed-down Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Simulation & Reconstruction Detectors: full transport in ITS, track references at TPC Rin Primary Vertex: b* = 10 m  sx = sy = 50 mm, as expected for the 2007 run Reconstruction: TPC tracking response parametrized (old parametrization from 2002  conservative efficiencies and resolutions) Slow Points in ITS z of vertex from SPD Kalman in ITS with AliITStrackerV2 full vertex reco with tracks NOT INCLUDED (to be done before analysis) Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

TPC parametrization TPC param / full tracking full tracking TPC param Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Reco & Sele TO-DOs TO DO for single-track cuts (pt and d0): - estimate CPU time, signal and background efficiency vs cut values - estimate cut values compatible with “final” candidate cuts TO DO for secondary vertex: implement vertex fitting with errors and c2 (as done for primary) TO DO for inv. mass analysis: prepare fit procedure/code; take into account reflections in fit; background subtraction IN PROGRESS, talk on Friday IN PROGRESS Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese

Corrections & Errors TO-DOs TO DO for beauty feed-down: - define procedure to generate MC with B -> D0, and reweight results according to a given pQCD dsb/dpt - define procedure to use ALICE single m measurement to infer B production in the barrel TO DO for systematic errors: - define procedure for embedding (how many {pt,y} bins? needed MC stats? which real events? vs dNch/dy? vs zvertex?) - define procedure to evaluate d0 resol. from data IN PROGRESS Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese