terzo convegno sulla fisica di alice, lnf, 13.11.2007 andrea dainese 1 andrea dainese (infn lnl)...
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Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 1
Andrea Dainese Andrea Dainese (INFN LNL)(INFN LNL)
Hadronic Charm:Hadronic Charm:Introduction & DIntroduction & D00KK
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 2
Invariant mass analysis and significance maximization (in bins of pt, y, RP…)
Analysis SchemeEvent reconstruction (RAW ESD AOD)
Charm “production” (ESD/AOD AOD for D’s)
D0 signal selection (using PID and geom/kinem cuts)
Correction for efficiencies, acceptance, BR
KDselectedN 0
1||
0
yt
Dproduced
dydp
dN
Cross section normalisation1||
0
yt
D
dydp
d
Physics (& comp. with theory)
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 3
Heavy-quark production at the LHCBaseline 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 --
[mb] QQNNQQ
totN
Theoretical uncertainty of a factor 2-3
MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.
98EKSshadowingC
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 4
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 5
Invariant mass analysis and significance maximization (in bins of pt, y, RP…)
Analysis SchemeEvent reconstruction (RAW ESD AOD)
Charm “production” (ESD/AOD AOD for D’s)
D0 signal selection (using PID and geom/kinem cuts)
Correction for efficiencies, acceptance, BR
KDselectedN 0
1||
0
yt
Dproduced
dydp
dN
Cross section normalisation1||
0
yt
D
dydp
d
Physics (& comp. with theory)
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 6
Event reconstruction (RAW ESD AOD)
Reconstruction in the barrel tracksStandard AOD (Analysis Object Data), extracted from ESD (Event Summary Data):
Set of TLists:
AliAODHeaderPart of the event Meta Data, e.g.:• run #, event #, field, trigger, event tags
Global event information, e.g.:• centrality, multiplicity
chargedtracks
V0
(K0S,)
jets & 0
Set of TLists:
AliAODHeaderPart of the event Meta Data, e.g.:• run #, event #, field, trigger, event tags
Global event information, e.g.:• centrality, multiplicity
chargedtracks
V0
(K0S,)
jets & 0
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 7
PrimaryVertex B
e
Xd0
rec. track
The key issue for HF reco: track impact parameter
Distance of closest approach to the primary vertex
At “high” pt: d0 c HF decay tracks displaced by ~100 m
ALICE ITS with SPD
< 60 m (r)for pT > 1 GeV/c
BA, CT, LNL, PD
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 8
Track impact parameter measurement in pp collisions
Track impact parameter resolution: d0 = vtx track
Vertex reconstructed from tracks (LNL, To)
Bias (underestimate of d0) if the considered track is used for vertex fit: of d0 distribution for primaries
m
bias!
bias!
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 9
Effect of ITS misalignment on d0 resolution
Impact parameter resol:
track = 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)
nullresidualfullfull+
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 10
Invariant mass analysis and significance maximization (in bins of pt, y, RP…)
Analysis SchemeEvent reconstruction (RAW ESD AOD)
Charm “production” (ESD/AOD AOD for D’s)
D0 signal selection (using PID and geom/kinem cuts)
Correction for efficiencies, acceptance, BR
KDselectedN 0
1||
0
yt
Dproduced
dydp
dN
Cross section normalisation1||
0
yt
D
dydp
d
Physics (& comp. with theory)
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 11
Analysis scheme (ESD/AOD ➔ AOD)
Set of TLists:
AliAODHeaderPart of the event Meta Data, e.g.:• run #, event #, field, trigger, event tags
Global event information, e.g.:• centrality, multiplicity
chargedtracks
V0
(K0S,)
jets & 0
Set of TLists:
AliAODHeaderPart of the event Meta Data, e.g.:• run #, event #, field, trigger, event tags
Global event information, e.g.:• centrality, multiplicity
chargedtracks
V0
(K0S,)
jets & 0
Standard AOD
Standard AOD+ HF vertices (15-20% in size)
Set of TLists:
AliAODHeaderPart of the event Meta Data, e.g.:• run #, event #, field, trigger, event tags
Global event information, e.g.:• centrality, multiplicity
chargedtracks
V0
(K0S,)
jets & 0
Set of TLists:
AliAODHeaderPart of the event Meta Data, e.g.:• run #, event #, field, trigger, event tags
Global event information, e.g.:• centrality, multiplicity
chargedtracks
V0
(K0S,)
jets & 02-prong
HF3-prong
HF...
ESDor
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 12
AliAnalysisVertexingHFsingle-track cuts on quality, pt (d0?)
[common cuts for all analyses]
build all (+,-) pairs and compute secondary vtx
create AliAODRecoDecayHF2Prong apply reco cuts
store D0
loop on all tracks (+ & -): build triplets, create AliAODRecoDecayHF3Prong,apply reco cuts (common for the 3 particles?)
loop on all tracks (+ & -) …create AliAODRecoDecayHF…
store D+, Ds+, c store D0
for D+,Ds+,c
+,D*+
for D0K
for D0K, J/ (from B)ee
store J/
tight D0 mass cutloop on all tracks for D*+ candidates
store D*+
Bari, Legnaro, Torino
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 13
x
pull
x
reso
lutio
n [
m]
Secondary vertex reconstructionTwo 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
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 14
Set of classes for storage and analysis of candidates
AliVParticle
AliAODRecoDecay
AliAODRecoDecayHFAliAODv0
AliAODRecoDecayHF2Prong AliAODRecoDecayHF3ProngD+,Ds,c,...D0,J/ from B,...
AliAODRecoDecayHF4ProngD0
PWG3PWG2
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 15
Invariant mass analysis and significance maximization (in bins of pt, y, RP…)
Analysis SchemeEvent reconstruction (RAW ESD AOD)
Charm “production” (ESD/AOD AOD for D’s)
D0 signal selection (using PID and geom/kinem cuts)
Correction for efficiencies, acceptance, BR
KDselectedN 0
1||
0
yt
Dproduced
dydp
dN
Cross section normalisation1||
0
yt
D
dydp
d
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 16
Selection Variables & PID
Variables:DCA: distance of closest approach between the two tracks
cos*: cosine of decay angle
d0xd0: product of the two tracks r impact parameters
cospointing: cosine of pointing angle
3 PID “modes” considered (TOF):keep all pairs (no PID)
keep only pairs with a K
reject only (,), (K,K)
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 17
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 18
Extraction of signal raw yield:Invariant mass analysis
Beware of reflections:
Reflections
Combinatorial
no PIDRS/TS~0.30 RS/TS~0.25 RS/TS~0.25
RS/TS~0.20 RS/TS~0.15 PID: (,), (K,K) rejected
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 19
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 (+- 3) = 39.7 +- 9.3 S/B (+- 3) = 85% SGNC as S/S (+- 3) = 4.3 (58 for 109 evts) SGNC as S/S+B (+- 3) = 4.3 ---------- From Simulation ------------ Total S integral (+- 3) = 39.5 S/B (+- 3) = 90% SGNC as S/S+B (+- 3) = 4.3 (59 for 109 evts)
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 20
0<pt<1 GeV/c
Significance maximization
Optimize cut values in pt bins: maximize significance in cut-variables space (e.g. 4D space)
Example:
2<pt<3 GeV/c3<pt<5 GeV/c5<pt<8 GeV/c
A.Rossi
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 21
Results
Checked performance w/o PID: not much worsening, but have to tighten cuts (larger systematic errors?)
pp (109 evts)
PPR
pp (109 evts)
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 22
Invariant mass analysis and significance maximization (in bins of pt, y, RP…)
Analysis SchemeEvent reconstruction (RAW ESD AOD)
Charm “production” (ESD/AOD AOD for D’s)
D0 signal selection (using PID and geom/kinem cuts)
Correction for efficiencies, acceptance, BR
KDselectedN 0
1||
0
yt
Dproduced
dydp
dN
Cross section normalisation1||
0
yt
D
dydp
d
Physics (& comp. with theory)
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 23
Corrections & Errors:Beauty feed-down (~10%)
Methods:
1. Monte Carlo with state-of-the-art pQCD input
2. use measurements from ALICE (from single , 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 24
Corrections & Errors:Acceptance, Reco & Selection EfficiencyMethod:
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, , 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 25
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 26
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 27
pt 0.4 GeV/c
primariesall
Evaluation of d0 res. from datapt 1.1 GeV/c pt 4.5 GeV/c
A.Rossi
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 28
Evaluation of d0 res. from data
Fit of all tracks’ d0 distr. in the range ~ (-3, +3) 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
d0=12m: OK!
no misal.
ITS
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 29
Invariant mass analysis and significance maximization (in bins of pt, y, RP…)
Analysis SchemeEvent reconstruction (RAW ESD AOD)
Charm “production” (ESD/AOD AOD for D’s)
D0 signal selection (using PID and geom/kinem cuts)
Correction for efficiencies, acceptance, BR
KDselectedN 0
1||
0
yt
Dproduced
dydp
dN
Cross section normalisation1||
0
yt
D
dydp
d
Physics (& comp. with theory)
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 30
Calibrating the probe (pp, s = 14 TeV)
D0 K
tpp
tAA
colltAA pN
pN
NpR
d/d
d/d1)( measured at 14 TeV, then
scaled by pQCD to 5.5 TeV
Expected sensitivity in comparison to pQCD:
1 year at nominal luminosity(109 pp events)
Detector configuration:ITS + TPC + TOF
~1 month
stat. err. vs # events
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 31
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 32
Heavy-to-light ratios
1 year at nominal luminosity(107 central Pb-Pb events, 109 pp events)
)()()(/ thAAt
DAAthD pRpRpR probes colour-charge dep.
of QCD energy loss
)()()( D from eB from e/ tAAtAAtDB pRpRpR
probes mass dep.of QCD energy loss
E loss calc.:Armesto, Dainese, Salgado, Wiedemann
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 33
Summary
Prepared software tools for reconstruction of (most) hadronic charm decays (+J/) 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...)
D0K: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 35
First pp data: machine scenario
* ~ 10 m (will be 0.5 m for Pb-Pb)
Bunch spread:
transverse bunch (*) ~ 70 m, long. bunch ~ 7.5 cm
Vertex spread:
transverse vertex =bunch/2~50 m, long. vertex = 5.3 cm
Luminosity: (1/vertex) ~1030 cm-2s-1 (70 kHz for pp = 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<<0.9, =)
First pp data: detector scenario
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 37
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 38
Beauty feed-down
Feed-down can be up to 15% after selection
Can use upper cut on |d0| to control it
To subtract it:1) use simulation with state-
of-the-art pQCD c and b predictions for LHC
2) later, use b cross section measured at LHC
3) later, use d0 of D0 to estimate feed-down
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 39
Simulation & Reconstruction
Detectors: full transport in ITS, track references at TPC Rin
Primary Vertex: * = 10 m x = y = 50 m, 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 40
TPC parametrization
full trackingTPC param
full trackingTPC param
full trackingTPC param
TPC param / full tracking
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 41
Reco & Sele TO-DOsTO 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 2 (as done for primary)
TO DO for inv. mass analysis: prepare fit procedure/code; take into account reflections in fit; background subtraction
IN PROGRESS
IN PROGRESS, talk on Friday
Terzo Convegno sulla Fisica di ALICE, LNF, 13.11.2007 Andrea Dainese 42
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 db/dpt
- define procedure to use ALICE single 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 dataIN PROGRESS