(2s) cross section and search for narrow resonances below the upsilon mesons at cdf

(2S) cross section and search for narrow resonances

below the Upsilon mesons at CDF

Alberto Annovi - INFN Frascati

for the CDF collaboration

International Workshop on Heavy Quarkonia 2008

Nara Women's University2-5 December 2008

Dec 4th, 2008 Alberto Annovi 2

The CDF detector @ Fermilab

Silicon Microstrip Tracker

Drift Chamber

Central Muon ||<0.6

Solenoid

Muon Extension ||<1.1

Calorimetersystem

Ｔｅｖａｔｒｏｎp pbar ＠ 1.96 ＴｅＶ


(2S) cross section


Why (2S) cross section?

Charmonium production as test of QCD models

NRQCD can account for J/ and (2S) cross-section

NRQCD *not* able to describe polarization

(2S) is clean: small feed-down from higher charmonium states

Extend differential xsec up to 30 GeV

Phys. Rev. Lett. 99, 132001 (2007)


Measurement principle

Select a clean di-muon sample Unbinned fit to separate

signal from backgrond prompt (2S) from long lived ones fit in pT bins

Calculate acceptance, efficiency and luminosity

Get differential cross-section:


Data selection

1.1 fb-1 from low-pT dimuon trigger Trigger selection

2 central muons pT > 1.5 GeVOff-line selection

2 central muons pT > 2 GeV 3 r- silicon (SVX II) hits / muon tracks, muons and vertex quality cuts

Analysis kinematical limits 2 GeV < pT((2S)) < 30 GeV | y((2S)) | < 0.6


Fitting the data Unbinned maximum likelihood fit variables

reconstructed mass reconstructed ct

Signal likelihood mass: Gaussian + crystal ball function ct (prompt): double Gaussian ct (long lived): exponential conv. Gaussian

Background likelihood mass: 1st order polynomial ct : combination of prompt, long lived symmetric and

long lived asymmetric

ct Lxy

pT /meffective ct:only ’ is

reconstructed


Fit projections

5.5 < pT < 6.0 GeV

5236 (2S)signal events

4213 prompt1023 long liv.signal events

CDF preliminary 1.1fb-1 CDF preliminary 1.1fb-1


Acceptance and efficiency

Geometric acceptance from CDF simulation (2S) generated uniform in , pT and y (2S) decayed with EVTGEN

different polarization are generated

Trigger efficiency measured on data Offline reconstruction efficiency

measured on data in combination with MC Nominal luminosity 1.1fb-1

effective luminosity is 0.95fb-1

due to trigger dynamic prescale @ high luminosity


Polarization Acceptance depends upon polarization

Acceptance and its systematics are determined assuming: prompt : = 0.01 ± 0.13

A=2% @ pT=3 GeV A=20% @ pT=23 GeV

from B decays eff = 0.35 ± 0.25 ± 0.03 A=1.5% @ pT=3 GeV A=19% @ pT=23 GeV

Inclusive measurement uses weighted average acceptance

dN

dcos1 cos2

Phys. Rev. Lett. 99, 132001 (2007)


Systematics uncertanities


Differential cross-section

CDF preliminary 1.1fb-1

pp (2S)X Br (2S) 3.28 0.06(stat.) 0.31(syst.)nb

2 < pT((2S)) > 30 GeV | y((2S)) | < 0.6

Inclusive total cross-section:

pp (2S)X Br (2S) 2.62 0.05(stat.) 0.25(syst.)nb

Prompt component tot. xsec:

preliminary


Comparison with Run I

Run II (1.96TeV) pointscentered on bin <pT>.

Run I (1.8TeV) points areon bin centers.

B decay points scaleddown by 0.1



Ratio of cross-sections

PRD to be submitted soon

Ratio of (2S) to J/ Ratio of ratio

CDF preliminary 1.1fb-1 CDF preliminary 1.1fb-1

http://www-cdf.fnal.gov/physics/new/bottom/071018.blessed-psi2S-xsec/

prompt

longlived


Comparisons with NNLO*

Theory curve courtesy of P. Artoisenet et al., according to Phys.Rev.Lett.101:152001,2008. [arXiv:0806.3282]see also proceedings for HP2008 submitted to EPJC

Yield better described at low-pT.High-pT data (>17 GeV) from this measurement not compatible with theory.

Theory progress here is welcome!

NNLO* CSM


search for narrow resonances below the Upsilon mesons


Why looking for light dimuon resonances?

Low mass sbottom not completely excluded D.G. Aschman et al., Phys.Rev.Lett.39:124 (1977) A. M. Boyarski et al., Phys. Rev. Lett. 34, 762 (1975) CLEO, Phys. Rev. D 63, 051101 (2001) DELPHI, Phys. Lett. B 444, 491 (1998)

Some models include low mass sbottom M. Carena et al., Phys.Rev.Lett.86:4463 (2001) E. L. Berger et al., Phys.Rev.Lett.86:4231 (2001)


Dimuon spectrum in Run I data

G. Apollinari et al.using CDF Run I data

Phys.Rev.D72:092003,2005

3.5 excess


Analysis method

Search for prompt dimuon pairs look for resonances (epsilon) with detector resolution

Report results as *BR relative to Y(1S) Leptonic width of hypotetical sbottomonium

Assumptions for *BR relative to Y(1S) Assume to be unpolarized Assume pT

to scale with mass w.r.t. (1S) i.e. <pT

>/ <pTY(1S)> = mEpsi/ mY(1S)

Assume to be prompt Not produced inside a jet, i.e. isolated


Data sample

630pb-1 from dimuon trigger June 2006 - January 2007

Trigger selection 1st central muon pT > 3 GeV, || < 0.6

2nd muon pT > 2 GeV, || < 1.1


Data selection

First reconstruct all dimuon candidates passing trigger confirmation

Data contains a large contamination of dimuons from bbbar and ccbar

Require isolation < 4 GeV for both muons Isolation is sum of all tracks pT in a cone around each muon

Promptness cuts on 3D vertex Vertex probability > 0.001 Lxy/xy < 3 (Lxy w.r.t primary vertex)

Isolationtracks

pT<4GeV

2 2 r 0.4


Dimuon mass spectrum


Upsi region fit

Fit withBkg: 5th degree polynomialSig: Double Gaussians

Fit results52780 ± 350 Y(1S) eventsbkg of 13976 events

9.3 < M < 9.55 GeVMY(1S) 9459 ± 1 MeVM 52 ± 1 MeV


Resonance search

2/NDF 66/55Probability 0.14

Background only: 5th degree

polynomial fit


Resonance search

Add a Gaussian to the fit We fit in the region 6 to 9.1

GeV

perform 108 fits in steps of 25MeV starting at 6.3 GeV

Peak width is fixed to expectations from simulation:

40 to 48 MeV

Probe Gaussian in blue


Upper limits

90% Bayesian limits assuming prior probability flat above zero acceptance correction is

Arel=65.5% of Y(1S) at 6.3 GeV Arel=97.4% of Y(1S) at 9.0 GeV

N

bayes

NY (1S )

Arel

Where N is number of reconstructed events


Upper limits

90% CL

Red is expected limit. Blue is observed limit.

Systematic is 6% relative acceptance due to Y polarization resonance line shape modeling

The excess in PRD72:092003,2005was (36±9)*10-3

at 7.2 GeV


Upper limits

90% CL 90% CL

Sbottomoniumleptonic width

http://www-cdf.fnal.gov/physics/new/bottom/080703.blessed-Dimuon_resonance/


Conclusions

(2S) cross section in Run II provides data up to 30 GeV for the first time adds input for quarkonia production understanding

Search for narrow resonances below the Upsilon mesons no evidence for new signals --> set limits almost exclude light sbottomonium (6.3 < m < 9 GeV)

not fully excluded within (not shown) theoretical uncertainties


BACKUP


Comparison with Run I

Run II (1.96TeV) pointsscaled to 1.8 GeV (-14%)centered on bin <pT>.

Run I (1.8TeV) points areon bin centers.

NRQCD uses a fit to Run I data described inE. Braaten et. Al., hep-ph/0008091Phys.Rev.D63:094006,2001


(2s) cross section and search for narrow resonances below the upsilon mesons at cdf

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