L c + Status Report
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Transcript of L c + Status Report
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08-Mar-0508-Mar-05
STAR
cc++ Status Report Status Report
Heavy Flavor Working GroupHeavy Flavor Working Group
Manuel Calderon de la BarcaManuel Calderon de la Barca
Indiana UniversityIndiana University
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Why? How?Why? How?
cc++ : lightest charmed baryon. : lightest charmed baryon.
Never measured in heavy ion collisions before.Never measured in heavy ion collisions before. ~15 – 20% of charm production goes into ~15 – 20% of charm production goes into cc
++.. If (signal) then {yield? spectra? Centrality dep?}If (signal) then {yield? spectra? Centrality dep?}
Does recombination work for charm as well?Does recombination work for charm as well?
cc++p Kp K-- ++ (+ c.c. mode for (+ c.c. mode for cc
--)) M = 2.285 GeV, BR (5 M = 2.285 GeV, BR (5 ± ± 1.3) %, c1.3) %, c=60 =60 m, (udc)m, (udc)
3-body decay: large combinatorical background3-body decay: large combinatorical background Momenta of daughters in good PID regionMomenta of daughters in good PID region
Maybe there’s a chance?Maybe there’s a chance?
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR GEANT SimulationsGEANT SimulationsOverall acceptance = 17%Overall acceptance = 17%Acc == (all 3 daughters leave 10 hits in TPC)Acc == (all 3 daughters leave 10 hits in TPC)
Thrown
Accepted
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR GEANT AcceptanceGEANT Acceptancevs. pvs. pTT (~20% at 1 GeV/c), vs. y (~40% at y=0) (~20% at 1 GeV/c), vs. y (~40% at y=0)
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Where are the daughters?Where are the daughters?
Pion Kaon Proton
Original <pt>Original <pt> Accepted <pt>Accepted <pt>
0.3760.376 0.3850.385
KK 0.4950.495 0.5830.583
pp 0.5970.597 0.6770.677
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Rough Yield EstimateRough Yield Estimate cc/(D/(D00+D+D++) = 0.3, D) = 0.3, Dss/(D/(D00+D+D++) = 0.2) = 0.2 If If cccc==DDDD + + cc + + DsDs then then
cc//cccc = 0.2 = 0.2 If If cccc=600 =600 b and :b and :
TTaaaa=23 mb=23 mb-1-1 for 10% central for 10% central TTaaaa=5.5 mb=5.5 mb-1-1 for minbias for minbias i.e. assuming binary collision scalingi.e. assuming binary collision scaling
ccbar yield per 10% central = .023 x 600 = 14 ccbar yield per 10% central = .023 x 600 = 14 ccbar yield per minbias = .0055 x 600 = 3.3 ccbar yield per minbias = .0055 x 600 = 3.3
cc++ yield per 10% central = 14x0.2x0.5 = 1.4 yield per 10% central = 14x0.2x0.5 = 1.4
cc++ yield per minbias = 3.3x0.2x0.5 = 0.33 yield per minbias = 3.3x0.2x0.5 = 0.33
Branching ratio 5%: 1.4x0.05=0.07 central, 0.33x0.05=1.65 e-2Branching ratio 5%: 1.4x0.05=0.07 central, 0.33x0.05=1.65 e-2 Accepted Accepted cc
++ = 0.07 x 0.17 = 0.012 central, 2.8 e-3 minbias = 0.07 x 0.17 = 0.012 central, 2.8 e-3 minbias Efficiency 0.8 (single track) : .012x(0.8Efficiency 0.8 (single track) : .012x(0.833) = .006 central, 1.44 e-3) = .006 central, 1.44 e-3 1 1 cc
++ in the right decay mode in our acceptance per 200 10% central events. in the right decay mode in our acceptance per 200 10% central events. 1 1 cc
++ in 1000 minbias events. in 1000 minbias events.
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Analysis CutsAnalysis Cuts
Fit points >=24Fit points >=24dE/dx points >=20dE/dx points >=20Dca < 1.5 cmDca < 1.5 cm |h|<1.0|h|<1.0PID cuts:PID cuts: |nSigma_X|<1 && |nSigma_Y|>3 && |nSigma_Z|>3|nSigma_X|<1 && |nSigma_Y|>3 && |nSigma_Z|>3
Where x,y,z == pion,kaon,protonWhere x,y,z == pion,kaon,proton
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR PID ChecksPID Checks
Few events
Hey, what’s all this stuff??
Deuterons visible, other tracksare possible merged tracks, but theircontribution is small.
More events!
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Data: pt of candidate daughtersData: pt of candidate daughters
This is the right kinematic range for the This is the right kinematic range for the cc++..
Can we beat the background?Can we beat the background?
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Invariant mass plots central.Invariant mass plots central.
Background estimate from 3.2 M central events.Background estimate from 3.2 M central events. 23 counts per event: S/B = 0.006/23 = 2.6x1023 counts per event: S/B = 0.006/23 = 2.6x10-4-4
For a 3For a 3 signal, need : 9 x 2(3833) = 69K signal, need : 9 x 2(3833) = 69K cc++
NNeventsevents = 69K/0.006 = 11.5 M central events = 69K/0.006 = 11.5 M central events (sufficient in Run IV)(sufficient in Run IV)
(Signal) (Signal)
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Invariant mass plots (minbias).Invariant mass plots (minbias).
Background estimate from 118K minbias events.Background estimate from 118K minbias events. 12 counts per event: S/B = 0.00144/23 = 6.2x1012 counts per event: S/B = 0.00144/23 = 6.2x10-5-5
For a 3For a 3 signal, need : 9 x 2(16014) = 288K signal, need : 9 x 2(16014) = 288K cc++
NNeventsevents = 288K/0.006 = 48 M minbias events = 288K/0.006 = 48 M minbias events (not sufficient in Run IV)(not sufficient in Run IV)
(Signal) (Signal)
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Background subtractionBackground subtraction If we flip the sign of the pion, can that give us a If we flip the sign of the pion, can that give us a
background histogram if background histogram if +/+/- = 1 ?- = 1 ?
Doesn’t work!
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Why doesn’t it work?Why doesn’t it work?Ratio is not exactly 1.Ratio is not exactly 1.
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR +/+/- expanded scale- expanded scale
Ratio not flat and not =1 to few per mil.Ratio not flat and not =1 to few per mil. Important when need to model background in millons of events!Important when need to model background in millons of events!
Contamination above 0.6 GeV plays a role.Contamination above 0.6 GeV plays a role.
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR Fitting the shape.Fitting the shape.
Approach: Approach: polinomial fit in 2.1 < M < 2.5polinomial fit in 2.1 < M < 2.5Add a gaussian and see if chi2 improves.Add a gaussian and see if chi2 improves.
(for later, i.e. no signal there, statistics is still too low.)(for later, i.e. no signal there, statistics is still too low.)
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR
In pT bins, does subtraction work?In pT bins, does subtraction work?
pK+- (c+)
0<pt<0.53.6 M Central Events
pK-+ (c-)
1<pt<1.53.6 M Central Events
Subtraction of pol6 fit.Invariant mass.
2/dof=0.99
2/dof=0.79
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08-Mar-0508-Mar-05 Manuel Calderon de la BarcaManuel Calderon de la Barca
STAR ConclusionsConclusions
From rough signal and background numbers, From rough signal and background numbers, possible signal in Run 4possible signal in Run 415 M events for ~315 M events for ~3 signal in central events. signal in central events.
To do:To do:Process data as it comes, check for pt dependence.Process data as it comes, check for pt dependence.Will process minbias, central events.Will process minbias, central events.