Quarkonia Production & Polarization at CDF

Quarkonia Quarkonia Production & Polarization Production & Polarization

at CDFat CDF

Min Jeong Kim, Carnegie Mellon UniversityMin Jeong Kim, Carnegie Mellon University(For the CDF Collaboration)(For the CDF Collaboration)

International Workshop on Heavy Quarkonium 2006 @ BNL, June 27-30

06/29/2006 International Workshop on Heavy Quarkonium 2

OutlineOutline Today’s presentation is limited to the charmonium production.

Charmonium production at Tevatron:Charmonium production at Tevatron: - prompt (direct & feeddown from heavier states)- prompt (direct & feeddown from heavier states) - decay of B-hadrons- decay of B-hadrons

Introduce three CDF Run II analyses related to the topic of charmonium production: - A Measurement of the J/ Spin Alignment - Measurement of the ’ Polarization - Relative Production of the c1(1P) and c2(1P)


Theory MotivationTheory Motivation A large excess (A large excess (××50) of J/50) of J/ & & (2S) production compared with predictions f(2S) production compared with predictions f

rom the rom the Color Singlet Model (CSM); Color Singlet Model (CSM); difference in the pdifference in the pTT spectrum. spectrum.

[PRL 79, 572 (1997), PRD 71, 032001 (2005)] [PRL 79, 572 (1997), PRD 71, 032001 (2005)] Prediction based on the CSM: prompt J/Prediction based on the CSM: prompt J/ production should be dominated production should be dominated

((>>90%) by feeddown from 90%) by feeddown from cc production. However, CDF Run I measuremen production. However, CDF Run I measuremen

t [PRL 79, 578 (1997)] shows that t [PRL 79, 578 (1997)] shows that ~~30% of prompt J/30% of prompt J/ production came fro production came from m cc..

Nonrelativistic QCD (NRQCD) addresses the discrepancy between Nonrelativistic QCD (NRQCD) addresses the discrepancy between data and the CSM by introducing the data and the CSM by introducing the Color Octet MechanismColor Octet Mechanism with adjustable hadronization parameters that allow it to match with adjustable hadronization parameters that allow it to match the observed pthe observed pTT-dependence and amplitude of production.-dependence and amplitude of production. Prediction based on NRQCD: the J/Prediction based on NRQCD: the J/ mesons should be produced mesons should be produced with transverse polarization at large pwith transverse polarization at large pTT ( (>> 15 GeV/c). The Run I 15 GeV/c). The Run I data did not show such an effect, but the amount of data in the region data did not show such an effect, but the amount of data in the region where the model expected to work well, were not sufficient enough where the model expected to work well, were not sufficient enough to make a definite conclusion. [PRL 85, 2886 (2000)] to make a definite conclusion. [PRL 85, 2886 (2000)]


PolarizationPolarization

Transverse ( Longitudinal: (

angle between + in the J/ rest frame & J/ in the lab frame.

Zero polarization (= 0) means that all 3 helicity states are equally populated.

Angular distribution depends on the polarization parameter

11 cos1cos

*2*

d

dΓ


J/J/ Candidate Selection Candidate Selection Reconstruct J/ from 800 pb-1 of data collected using the CDF central dimuon trigger: 5 ≤ pT(GeV/cy| < 0.6.

Identify muons using the COT (central outer tracker), SVX II (silicon vertex detector) and CMU (central muon system). --- Overview of CDF detector was given by M. Aoki on Tuesday.---

Select baseline samples with pT > 1.75 GeV/c requirement to minimize biases due to trigger turn on.

Separate into prompt or B-decay candidates using the impact parameter information of two muons:

MC studies show Prompt: S ≤ 8, B-decay: S > 16

2

μ

0

2

μ

0

00

μμ

dd

ddS


J/J/ Candidates Candidates

Mass fit: double Gaussian signal plus linear background Signal region: (M-3, M+3) Lower sideband (M-13, M-10) is further displaced from the nominal J/ mass than upper-sideband (M+5, M+8), to avoid any effects from the radiative tail of J/ mass distribution. Extract decay angular distributions from the events in signal and sideband (background) regions. Divide candidates into 6 pT bins for polarization measurement.


Residual Background (Contamination)Residual Background (Contamination)

Assumption: prompt Gaussian signal is centered at ct = 0 and symmetric.

Estimate using the sideband-subtracted ct distributions

Introduce ct > 0.03 cut to further reduce the prompt contamination.

All Events

PromptEvents

B-decayEvents

B-decay EvtsPromptGaussian

Mis-measuredEvts


Residual Heavy Flavor ContaminationResidual Heavy Flavor Contamination

Percentage B fraction fB comparison between ours and published analysis [PRD 71, 032001 (2005)]:


MC TemplatesMC Templates

Getting detector trigger acceptance right is crucial: use experimentally-derived acceptance function. Angular resolution is very important: CDF cos resolution < 0.01 for all pT. Raising the muon threshold reduces cos * range.

6/GeVJ/ψ5 cpT


Polarization of J/Polarization of J/ Mesons from B-decays Mesons from B-decays

Our measurement is consistent with both Run I and BaBar. We differ from BaBar only by 1.2. CDF data are influenced by Bs and B-baryon contributions that are not seen at B-factories.

Combine 6 bins by a 2 average;

aB = -0.066 0.050

Prob (2) = 18 %

B = -0.1 0.1 (CDF Run I)B = -0.129 0.009 (BaBar measurement adapted to the CDF environment in Run II)

Polarization for B-decay events should be independent of pT.


Prompt J/Prompt J/ Polarization Results Polarization Results

fit is corrected for the residual heavy flavor using B measured:

B

BB

B

B

1

fitprompt


Systematic StudiesSystematic StudiesAll systematic effects are small compared to the statistical errors.

We also investigated other possible systematics:

- cos binning effect - different signal and background extraction method - run dependence (detector and trigger issues) - dependence of different pTrequirements

No significant effects are found.


′′PolarizationPolarization

Same theoretical framework applies to prompt ′ and J/ production. ′ is a cleaner system than J/; no contributions from feeddown from higher states. This analysis uses ′events from CDF central dimuon trigger. This ′ sample has 10× more events than the Run I sample. ′uses same analysis method just described for J/


′′ PolarizationPolarization< B-decay polarization >

< prompt polarization >

First measurement of B for ′:

03.027.028.0 BWithin statistics, it could be same as for J/ but the central value is transverse.

Prompt polarization agrees with Run I. Prompt alignment becomes longitudinal at high pT, just like J/ case.


Measurement ofMeasurement of ((c2c2)/)/((c1c1))

Models of prompt charmonium production in hadronic collisions alModels of prompt charmonium production in hadronic collisions always contain significant ways contain significant cJ cJ contributions.contributions.

Measurement of the properties of Measurement of the properties of cJcJ production has always been production has always been an experimental challenge.an experimental challenge. The relatively low energy photon from the The relatively low energy photon from the cJcJJ/J/, decay is diffic, decay is diffic

ult to measureult to measure Calorimeter measurements give good efficiency, poor resolutionCalorimeter measurements give good efficiency, poor resolution Conversion measurements give poor efficiency, good resolutionConversion measurements give poor efficiency, good resolution

The measurement of The measurement of ((c2c2) / ) / ((c1c1) has been performed at several en) has been performed at several en

ergies and beam types over the years.ergies and beam types over the years. Best measurements have ~100 events, 30% statistical uncertaintBest measurements have ~100 events, 30% statistical uncertaint

y on the cross section ratio.y on the cross section ratio. Results like 1.0±0.3 are consistent with most models.Results like 1.0±0.3 are consistent with most models.


cJcJ Data SetData Set Here we reconstruct:Here we reconstruct:

cJcJJ/J/, J/, J/++--, , ee++ee--

Same events used for polarizatiSame events used for polarization analysis.on analysis.

Conversion reconstruction of thConversion reconstruction of the photon gives excellent energy e photon gives excellent energy (mass) resolution.(mass) resolution.

B/Prompt components are easilB/Prompt components are easily separated.y separated.

Simultaneous fit to the mass Simultaneous fit to the mass and flight distance distributions and flight distance distributions is used to extract the relative yieis used to extract the relative yields for both production mechanilds for both production mechanisms.sms.


Results on Results on ((c2c2)/)/((c1c1))

Prompt Production

For prompt production, we measFor prompt production, we measure (for pure (for pTT 4-20 Gev/c) 4-20 Gev/c)

This is a new level of precision fThis is a new level of precision for this measurementor this measurement

This should provide a nice constThis should provide a nice constraint on production models.raint on production models.

.).(06.0.)(03.0.)(04.070.0c1

c2

χ

χFBsysstat

Systematic uncertainties are small Systematic uncertainties are small for this ratio:for this ratio:

The dominant systematic uncertainty The dominant systematic uncertainty comes from the branching fractions:comes from the branching fractions:

CDF preliminary


ConclusionConclusion Measured alignments for prompt J/and ′ mesons are longitudinal in higher pT region; results disagree with NRQCD predictions, but agree with Run I measurement at the highest pT point. ′ polarization agrees with J/ pattern.

For convenient comparison, we restate the prompt production ratios as:

.).(13.0)sys.(07.0)stat.(08.043.1c2

c1

χ

χFB

Eur. Phys. J. C 39, 163 (2005); predict longitudinal polarization for pT(J/ > 15 GeV/c.


(Backup Slides)(Backup Slides)


Residual Heavy Flavor ContaminationResidual Heavy Flavor Contamination

Percentage B fraction fB

comparison between oursand published analysis[PRD 71, 032001 (2005)]

fother = 3.6 [%]

decayprompt

MCprompt /11

B

BotherB NN

εBNf


Polarization FitterPolarization Fitter An adaptation of the 2 fitter developed for the CDF Run I measurement.

Components that get into the polarization fit: - ND : total number of events in the signal region. - Di : cos * distribution for ND events. - NB : total number of events in the sideband regions. - Bi : cos * distribution for NB events. - Template angular distributions from Ti (transverse) & Li (longitudinal)

signal MC samples: include all the corrections due to acceptance and efficiency effects to the theoretical angular distributions.

[Run II measured J/ pT spectrum from PRD 71, 032001 (2005)] - BB : residual heavy flavor contamination

40 bins of 0.05 ( -1 < cos * < 1): i = 0 39

TiTiTTi pLpTpNpES 1;

i i TiTi

i TiTiT pLpT

pBpDpN

1

;


MC TemplatesMC Templates

Acceptance depends on the polarization; acceptance is lower in T case.

Raising the pTcut reduces discrimination between T & LPolarization, especially at lowpT(J


Polarization of J/Polarization of J/Mesons from B-decaysMesons from B-decays

The remaining contamination is corrected with the zero polarization assumption.


Prompt J/Prompt J/ Polarization Results Polarization Resultsfit is corrected for theresidual heavy flavorusing B measured:

B

BB

B

B

1

fitprompt


Prompt J/Prompt J/ Data DataC Comparison of C Comparison of Muon pMuon pTT Spectrum Spectrum

The influence of the J/ spin alignment to the pT spectrumof muons.

The polarization dependence on low-pT muon is largestat low pT(J bin.

Prob (2) = 27 % Prob (2) = 68 %

Good agreement between dataand MC tuned to match themeasured polarization in thelowest pT bin of J/ with muonpT cut of 1.6 GeV/c.

-+

+ -

Documents

Quarkonia Production & Polarization at CDF