First measurement of the ratio b l b l c mu b l b l c p at cdf
Download
1 / 28

First Measurement of the Ratio B ( L b  L c mu )/ B ( L b  L c p ) at CDF - PowerPoint PPT Presentation


  • 65 Views
  • Uploaded on

First Measurement of the Ratio B ( L b  L c mu )/ B ( L b  L c p ) at CDF. Shin-Shan Yu University of Pennsylvania SLAC Experimental Seminar, August 11th, 2005 http://www-cdf.fnal.gov/physics/new/bottom/050407.blessed-lbbr/. Outline. L b. udb. Why L b CDF Detector, Trigger

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'First Measurement of the Ratio B ( L b  L c mu )/ B ( L b  L c p ) at CDF' - eyal


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
First measurement of the ratio b l b l c mu b l b l c p at cdf

First Measurement of the Ratio B(LbLcmu)/B(LbLcp)at CDF

Shin-Shan Yu

University of Pennsylvania

SLAC Experimental Seminar,August 11th, 2005

http://www-cdf.fnal.gov/physics/new/bottom/050407.blessed-lbbr/


Outline
Outline

Lb

udb

  • Why Lb

  • CDF Detector, Trigger

  • Lb Relative Branching Fractions

Shin-Shan Yu


Big picture why l b baryon
Big Picture : Why Lb Baryon?

u d b

Shin-Shan Yu


Experiment b l b l c mu b l b l c p
Experiment B(LbLcmu)/B(LbLcp) ?

and

  • Relative BR is the yield ratio corrected for the efficiency, e.g:

  • Four charged tracks in the final state

  • Data come from the same trigger, most systematics cancel.

  • Control samples: similar decays in the B meson system

But since we can not reconstruct neutrinos, several backgrounds can fake our semileptonic signals in the data ….

Shin-Shan Yu


Cdf detector trigger
CDF Detector & Trigger

  • Silicon Tracker

    • || < 2

    • svertex ~ 30 mm

  • Central Outer Tracker (COT)

    • 96 layers drift chamber, up to ||~1

    • sPT/PT~ 0.15% PT

  • Central Muon Chamber

    • 4 layers drift chamber outside the calorimeter

    • || < 0.6

  • Two Displaced-track Trigger

    • pT > 2 GeV/c, 120 m ≤ d0≤ 1 mm,

    • Lxy> 200 m,S pT > 5.5 GeV/c

    • 150 M events analyzed for this measurement

Shin-Shan Yu


Signal sample l b l c x l c p k p
Signal SampleLbLcXLc p+ K-p+

Hadronic Signal

Background shapes come from MC

c2/NDF=36.6/42

Prob=70.7%

Inclusive Semileptonic Signal

Shin-Shan Yu


Control sample b 0 dx d k p p
Control SampleB0 DX, D+ K-p+ p+

Inclusive Semileptonic Signal

Hadronic Signal

Background shapes come from MC

Shin-Shan Yu


Control sample b 0 d x d d 0 p d 0 k p
Control SampleB0 D*X, D*+ D0p+, D0 K-p+

Inclusive Semileptonic Signal

Hadronic Signal

Background shapes come from MC

Shin-Shan Yu


Mc and data comparison before
MC and Data Comparison: Before

  • We used MC to obtain relative efficiencies of signals and backgrounds.

  • Compare MC and background subtracted signal distribution in the data.

  • Tune our MC if MC and data disagree, e.g: PT(Lb), M(Lcm)

PT(Lb)[GeV/c]

M(Lcm)[GeV/c2]

Shin-Shan Yu


Mc and data comparison after
MC and Data Comparison : After

Shin-Shan Yu


Where are the semileptonic backgrounds from
Where Are the Semileptonic Backgrounds from?

  • Physics Background

    • b-hadron -> …. -> Lcm + additional particles e.g:

    • Reduced by the M(Lcm) cut

  • Normalize the amount to the measured hadronic signal

    • BRs come from PDG, theoretical estimate and preliminary measurements

  • ~10% contribution

Shin-Shan Yu


First observation of l b semileptonic background
First Observation of Lb Semileptonic Background

CDF Run II Preliminary 360 pb-1

Sc++

Lc(2625)

Lc(2593)

Sc0

Sc++,+,0

CDF Run II Preliminary 360 pb-1

CDF Run II Preliminary 360 pb-1

Lc(2625)

Lc(2593)

  • Estimated BR of the reconstructed background based on the first observation

  • PDG BR(Lb -> LcmX)=9.2%

Shin-Shan Yu


How to obtain b l b l c p
How to ObtainB(Lb  Lc p)?

Consistent with the prediction 0.45% (Phys. Lett. B586, 337)

  • Make use of previous CDF measurements

  • Lb MC PT spectrum using fully reconstructed decay was not available for CDF I

    • Correct the CDF I flambdab/fd using measured PT spectrum

      • Acceptance correction

      • Different PT thresholds affect the ratio 10 GeV/c vs. 6 GeV/c

Shin-Shan Yu


How to obtain b l b l c p1
How to ObtainB(Lb  Lc p)?

Shin-Shan Yu


Where are the semileptonic backgrounds from1
Where Are the Semileptonic Backgrounds from?

m?

  • Muon Fakes

    • p, K, p fake muons

    • ct and muon d0 cuts suppress prompt fakes

    • Our fakes mostly come from b decays

    • Weight “Lc+TRKfailm” events with the Pfake

    • p, K, p fractions from the inclusive B MC

    • ~5% contribution

Shin-Shan Yu


Where are the semileptonic backgrounds from2
Where Are the Semileptonic Backgrounds from?

  • QCD Pair Production:

    • charm and m from different b- or charmed hadrons

    • Suppressed due to the ct and PT(m) cuts

    • Rely on Pythia MC

    • Most sensitive to gluon splitting

    • ~0.2% contribution

p+

Lc+

Lc+

p+

Shin-Shan Yu



Consistency check
Consistency Check

Shin-Shan Yu


Dominant systematics
Dominant Systematics

  • Physics background and hadronic signal branching fractions

    • Measured: from PDG

    • Estimated:multiply the BR by 2 or 0

  • Mass fitting model

    • Vary the constant parameters in the fit

    • Several background shapes come from inclusive MC

      • vary BR of the dominant decays

  • MC modeling of acceptance and efficiency

    • pT spectrum

      • affect the efficiency and B (LbLcp)

    • Lb semileptonic decay model

      • size of the independent MC for reweighting the phase space distribution

      • uncertainty on the predicted form factors

Shin-Shan Yu


Uncertainty summary
Uncertainty Summary

Physics background and hadronic signal branching fractions

MC modeling of efficiency and acceptance

Shin-Shan Yu


Control sample result
Control Sample Result

Consistent with the 2004 world average 7.81.0 at the 1s level

Consistent with the 2004 world average 19.71.7 at the 0.7s level

New world average ratio 8.3  0.9

New world average ratio 19.1  1.4

Shin-Shan Yu


Signal sample result
Signal Sample Result

  • Experimental Uncertainties

  • dominated by:

    • Data sample size

    • B (LbLcp)

      • CDF Run I fbaryon/fd

      • B(Lc->pKp)

Shin-Shan Yu


What do we know about l b now
What Do We Know aboutLb Now?

(4.1  2.0) x 10-3

Lc l u (5.0  1.9) %

DELPHI

(Phys. Lett. B585, 63)

Lc l u/ Lc p 20.0  3.7

Lc(2593) +l u seen

Lc(2625)+l u seen

Sc++p-l u seen

Sc0p+l u seen

Shin-Shan Yu



q

ud

Shin-Shan Yu


Physics background
Physics Background calculation of b-hadron BR

Shin-Shan Yu


Mc tuning
MC Tuning calculation of b-hadron BR

Flat phase space

Form factor weighted

Shin-Shan Yu


L b polarization
L calculation of b-hadron BRb Polarization

Shin-Shan Yu


ad