Bottomonium results from babar
Download
1 / 36

BOTTOMONIUM RESULTS FROM BABAR - PowerPoint PPT Presentation


  • 277 Views
  • Updated On :

BOTTOMONIUM RESULTS FROM BABAR Veronique Ziegler (SLAC) Representing the BaBar Collaboration CharmEx 2009, Bad Honnef, Germany, Aug. 10-12 2009 OVERVIEW Observation of the Bottomonium Ground State, h b (1S), in U (3S) → g h b (1S) Decay

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 'BOTTOMONIUM RESULTS FROM BABAR' - liam


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
Bottomonium results from babar l.jpg

BOTTOMONIUM RESULTS FROM BABAR

Veronique Ziegler (SLAC)

Representing the BaBar Collaboration

CharmEx 2009, Bad Honnef, Germany, Aug. 10-12 2009


Overview l.jpg
OVERVIEW

  • Observation of the Bottomonium Ground State, hb(1S), in U(3S) → g hb(1S) Decay

  • Confirmation of the Observation of the hb(1S) in U(2S) → g hb(1S) Decay

  • Rb Scan above the U(4S)


Slide3 l.jpg

6580

DIRC

Charged particle ID by means of velocity measurement

DCH

Angles and positions of charged tracks just outside the beam pipe

Charged tracks momentum

dE/dx for PID

(1.5 T)

3.1 GeV

9.03 GeV [Y(4S)]

8.65 GeV [Y(3S)]

8.10 GeV [Y(2S)]


Babar run 7 dec 2007 apr 2008 pep ii e e asymmetric collider running at the u 2s 3s l.jpg

k

k

k

BaBar RUN 7 (Dec. 2007 – Apr. 2008)PEP-II e+e- Asymmetric Collider Running at the U(2S,3S)…

Effective

BABAR DATASETS:

~ 120 x 106Y(3S) events

≈ 20 X previous dataset (CLEO)

~ 100 x 106Y(2S) events

≈ 11 X previous dataset (CLEO)

~ 8.54 fb-1 above Y(4S)

≈ 30 X previous datasets (CLEO,

CUSB)

R-scan

4


Current picture of the bottomonium spectrum l.jpg

(nL) where n is the principal quantum number and L indicates the bb angular momentum in spectroscopic notation (L=S, P, D,…)

Current Picture of the Bottomonium Spectrum

threshold

hadrons

hadrons

[Orbital Ang. Momentum between quarks]

P-wave

S-wave


The h b 1s state l.jpg

The the bb angular momentum in spectroscopic notation (L=S, P, D,…)hb(1S) State

(11S0)


Slide7 l.jpg

Expected the bb angular momentum in spectroscopic notation (L=S, P, D,…)hb Production Mechanism

The U(nS) states are produced in hadronic interactions or from a virtual photon in e+e− annihilation

One of the expected production mechanisms of the hb(n’S) is by M1 (i.e. SS) transition from the U(nS) states [n’≤n]


The search for the h b at babar l.jpg
The Search for the the bb angular momentum in spectroscopic notation (L=S, P, D,…)hbat BaBar

  • Decays of hb not known  Search for hb signal in inclusive photon spectrum

    i.e. Search for the radiative transition Y(3S)→ghb(1S)

  • In c.m. frame:

    • For hb mass m = 9.4 GeV/c2 monochromatic line in Eg spectrum at 915 MeV, i.e. look for a bump near 900 MeV in inclusive photon energy spectrum from data taken at the U(3S)

√s = c.m. energy = m(Y(3S))

m = m(hb)


Slide9 l.jpg

ANALYSIS STRATEGY the bb angular momentum in spectroscopic notation (L=S, P, D,…)

  • Look for a bump near 900 MeV in the inclusive photon spectrum

    • Large background

      • Non-peaking components

      • Peaking components

  • Reduce the background

    • Selection Criteria

    • Optimization of Criteria

    • Optimization Check

  • Fitting Procedure

    • One-dimensional fit to the Eg distribution

      • Obtain lineshapes of the various components

      • Binned Maximum Likelihood Fit


Data sets l.jpg
DATA SETS the bb angular momentum in spectroscopic notation (L=S, P, D,…)

  • Y(3S) On-peak data

    • Full data sample: L = 28.6 fb-1

  • 122 x 106 Y(3S) events

    • Analysis sample: L = 25.6 fb-1

  • 109 x 106 Y(3S) events

  • expect ~ 20 x 103 Y(3S) g hb events

    • Test sample: L = 2.6 fb-1

  • 11 x 106 Y(3S) events

  • expect ~ 2 x 103 Y(3S) g hb events

    • Use since no reliable event generator for Y(3S) background photon simulation

  • Y(3S) & Y(4S) Off-peak data: L = 2.4 & 43.9 fb-1

L = Integrated Luminosity

(used for optimization

of selection criteria)

much smaller than expected background

(used for background studies)


The inclusive photon spectrum l.jpg
The Inclusive Photon Spectrum the bb angular momentum in spectroscopic notation (L=S, P, D,…)

  • Use ~9% of the Full U(3S) Data Sample

Look for a bump near 900 MeV in the inclusive photon spectrum

Non-Peaking background components:

~1/10 Y(3S) Analysis Sample

Large background

from cbJ(2P) decay

(next slide)


The inclusive photon spectrum12 l.jpg
The Inclusive Photon Spectrum the bb angular momentum in spectroscopic notation (L=S, P, D,…)

cbJ(2P) → g U(1S) (Peaking) background parametrization:

PDF: 3 Crystal Ball functions

relative peak positions and yield ratios are taken from PDF

Peaking background components (1):

U(3S)  cb0(2P)g softE(g soft) = 122 MeV

 U(1S) g hard E(g hard) = 743 MeV

U(3S)  cb1(2P)g softE(g soft) = 99 MeV

 U(1S) g hard E(g hard) = 764 MeV

U(3S)  cb2(2P)g softE(g soft) = 86 MeV

 U(1S) g hard E(g hard) = 777 MeV

U(3S)  cbJ(2P)g soft

(J=0,1,2)  U(1S) g hard

~1/10 Analysis Sample


The inclusive photon spectrum13 l.jpg
The Inclusive Photon Spectrum the bb angular momentum in spectroscopic notation (L=S, P, D,…)

Expected Signal

  • Very important to determine both lineshape and yield

    Depending on hb mass, the peaks may overlap!

Radiative return

to theU(1S)

,

e+e-→ gISR U(1S) (Peaking) background parametrization:

  • Estimate the expected yield using Y(4S) Off-Peak data [high statistics,

    no other peaking background near ISR signal], and

    extrapolating the yield to Y(3S) On-Peak data

~1/10 Analysis Sample

Peaking background component:

Radiative return from Y(3S)

to Y(1S): e+e-→ gISR Y(1S)

[ Eg = 856 MeV ]

ISR


U 3s g h b signal parametrization l.jpg

Crystal Ball lineshape the bb angular momentum in spectroscopic notation (L=S, P, D,…)

obtained from

simulated events

M.C.

U(3S)g hbSignal Parametrization

  • Fix signal Crystal Ball parameters from zero-width MC

  • Fix the S-wave Breit-Wigner width to 10 MeV

    • Fit the data with 5, 15, 20 MeV widths to study systematic errors


Slide15 l.jpg

Fit Result the bb angular momentum in spectroscopic notation (L=S, P, D,…)

Full data sample

L = 25.6 fb-1

 (109 ± 1) x 106 Y(3S) events

cbJ(2P)

~70000 events/ 5 MeV

15


Slide16 l.jpg

All backgrounds the bb angular momentum in spectroscopic notation (L=S, P, D,…)

subtracted

19152 ± 2010 events

The Observation of thehb

  • cbJ Peak Yield : 821841 ± 2223

  • gISR Y(1S) Yield : 25153 (fixed)

  • hb Yield : 19152 ± 2010

  • R(ISR/cbJ) ~ 1/33

  • R(hb/cbJ) ~ 1/43

Non-peaking

Background subtracted

gISR

hb


Study of systematic uncertainties l.jpg

  • No significant the bb angular momentum in spectroscopic notation (L=S, P, D,…)

    change !

STUDY OF SYSTEMATIC UNCERTAINTIES

  • Vary ISR yield by ± 1s (stat  5% syst) dN = 180, dEg =0.7 MeV

  • Vary ISR PDF parameters by ± 1sdN = 50, dEg =0.3 MeV

  • Vary Signal PDF parameters by ± 1s dN = 98, dEg =0.1 MeV

  • Vary cbJ peak PDF parameters by ± 1s dN = 642, dEg =0.3 MeV

  • Fit with BW width fixed to 5, 15, 20 MeV dN = 2010, dEg=0.8 MeV

  • Systematic uncertainty in the hb mass

    associated with the g energy calibration

    shift obtained from the fit to the cb peak dEg=2.0 MeV

    * Study of Significance

  • Vary BW width

  • Vary all parameters independently

  • Vary all parameters in the direction resulting

    in lowest significance

main source of systematic uncertainty in the hb yield

17


Summary of results l.jpg
Summary of Results the bb angular momentum in spectroscopic notation (L=S, P, D,…)

  • Signal Yield :

    • Estimate of Branching Fraction (expected transition rate):

  • Mass of the hb(1S):

    • Peak in g energy spectrum at

    • Corresponds to hb mass

    • The hyperfine (U(1S)-hb(1S)) mass splitting is


Slide19 l.jpg

The Search for the the bb angular momentum in spectroscopic notation (L=S, P, D,…)hb in

U(2S) → g hb(1S) Decay


Slide20 l.jpg

The Search for the the bb angular momentum in spectroscopic notation (L=S, P, D,…)hb in U(2S) → g hb(1S) Decay

Eg ~ 600 MeV

Eg ~ 400 ± 80MeV

Data Sample ~ 100 x 106U(2S) events

Similar analysis strategy in U(2S)→g hbas for U(3S)→g hb


Comparison of e g spectra l.jpg
Comparison of E the bb angular momentum in spectroscopic notation (L=S, P, D,…)g Spectra

Non-peaking

Background subtracted

U(3S) spectrum

Comparison with Y(3S) g hb Analysis:

☛ Better photon energy resolution at lower energy

 better separation between peaks

☛ More random photon background at

lower energy

 less significance at similar BF

U(2S) spectrum

21


Summary of h b results l.jpg
Summary of the bb angular momentum in spectroscopic notation (L=S, P, D,…)hb Results

  • hb mass:

  • Hyperfine splitting:

  • Combined mass is m(hb(1S)) = 9390.4± 3.1 MeV/c2

  • resulting in a hyperfine splitting of 69.9 ± 3.1 MeV/c2


Comparison of h b results with predictions l.jpg

Comparison of the bb angular momentum in spectroscopic notation (L=S, P, D,…)hb Results with Predictions

Compatible with predictions for hindered M1 transitions taking into account relativistic corrections

S. Godfrey, J.L. Rosner

PRD64, 074011 (2001)

Branching Fraction Values


Comparison of h b results with predictions24 l.jpg

x the bb angular momentum in spectroscopic notation (L=S, P, D,…)

□unquenched supercoarse

■unquenched coarse

□ unquenched fine

▲unquenched coarse

∆ unquenched fine

Comparison of hb Results with Predictions

  • Bottomonium spectrum has been computed in effective field theory of (potential) nonrelativistic QCD;

    in the next-to-leading logarithmic (NLL) approximation the Hyperfine splitting for charmonium,

    M(J/y)-M(hc)=104 MeV [B.A. Kniehl, et.al., Phys. Rev.Lett. 92, 242001 (2004)] is consistent with the experimental value, M(J/y)-M(hc)=117.7±1.3 MeV [CLEO]

  • For bottomium, non-perturbative contribution to Hyperfine splitting expected to be smaller than for charmonium

  • Nonrelativistic QCD NLL prediction: M(U(1S))-M(hb)=39±11(th)+9-8(das)MeV (das(MZ)=0.118±0.003)

  • Need proper description of QCD non-perturbative long distance effects...

  • Lattice QCD: unquenched prediction, M(U(1S))-M(hb)=61±14 MeV [A. Gray, et.al., Phys. Rev. D72, 094507 (2005)]

    Agrees well with BaBar measurement, M(U(1S))-M(hb)=80±10 MeV [T-W. Chiu, et.al., Phys. Rev.Lett. B651, 171 (2007)]

    * A.Penin [arXiv:0905.429v1] and private conversation with M. Karliner

Hyperfine Splitting *

A. Gray, et.al., Phys. Rev. D72, 094507 (2005)

HFS (MeV)


Slide25 l.jpg

R the bb angular momentum in spectroscopic notation (L=S, P, D,…)b Scan above theU(4S)


Energy scan above the u 4s l.jpg

cross section for the bb angular momentum in spectroscopic notation (L=S, P, D,…)

0th order cross section for

Energy Scan above the U(4S)

  • Motivation

    • Search for bottomonium states that do not behave as two-quark states (in analogy to Y(4260), Y(4350) and Y(4660) exotic states); such states would have a mass above the U(4S) and below 11.2 GeV.

  • Procedure

    • Precision scan in √s from 10.54 to 11.20 GeV

      • 5 MeV steps collecting ~25 pb-1 at each step (3.3 fb-1 total)

      • 600 pb-1 scan in energy range 10.96 to 11.10 GeV in 8 steps with unequal energy spacing (investigation of U(6S))

  • Measurement

    • Inclusive hadronic cross section

    • Search for unexpected structures in Rb(s)


Energy scan above the u 4s results l.jpg

s the bb angular momentum in spectroscopic notation (L=S, P, D,…)

s

Clear structures corresponding to the bb opening thresholds

Energy Scan above the U(4S): Results

Inclusive hadronic cross section measurement (PRL 102,012001 (2009))

Consistent with

coupled channel predictions


U 5s and u 6s mass and width measurement l.jpg
U the bb angular momentum in spectroscopic notation (L=S, P, D,…)(5S) and U(6S) Mass and Width Measurement

Fit with non-resonant amplitude & flat component added coherently with two interfering relativistic Breit-Wigner functions

Incoherent superposition of Gaussians and bckgr.

  • Compared to CLEO & CUSB,

  • BaBar has:

  • >30 x more data

  • 4 x smaller energy steps

  • Much more precise definition of shape

s

28


First observation of the h b 1s bottomonium ground state in the decay u 3s g h b 1s l.jpg
- First observation of the the bb angular momentum in spectroscopic notation (L=S, P, D,…)hb(1S) bottomonium ground state in the decay U(3S) → g hb(1S)

SUMMARY

- Confirmation from U(2S) →g hb(1S)

- Combined mass is m(hb(1S)) = 9390.4 ± 3.1 MeV/c2 and hyperfine splitting DMHFS = 69.9 ± 3.1 MeV/c2

- Precision scan of Rb in the energy range 10.54 < √s < 11.20 GeV yields parameters for U(5S) and U(6S), which differ from the PDG averages (also confirmed by Belle 's exclusive studies)


Back up slides l.jpg

BACK-UP SLIDES the bb angular momentum in spectroscopic notation (L=S, P, D,…)


Slide31 l.jpg

Bottomonium Transitions the bb angular momentum in spectroscopic notation (L=S, P, D,…)

  • U(nS) resonances undergo:

  • Hadronic transitions via p0, h,

    w, pp emission

  • Electric dipole transitions

  • Magnetic dipole transitions

    -- Allowed transition:

  • Electromagnetic transitions between the levels can be calculated in the quark model  important tool in understanding the bottomonium internal structure


Mass splittings in heavy quarkonia l.jpg

Hyperfine splitting the bb angular momentum in spectroscopic notation (L=S, P, D,…)

Fine splitting

S = 1

S = 0

Mass Splittings in Heavy Quarkonia

Triplet-Singlet mass splitting of quarkonium states

Mass splitting of triplet nP quarkonium states: cc,b(n3P0),

cc,b(n3P1),

cc,b(n3P2)

Non-relativistic

approximation

= 0 for L≠ 0 (→ 0 for r → 0), if long-range spin forces are negligible

≠ 0 for L=0

U(1S)-hb(1S) mass splitting meast.key test of applicability of perturbative QCD to the bottomonium system

6


Slide33 l.jpg

  • QCD Calculations of the η the bb angular momentum in spectroscopic notation (L=S, P, D,…)b mass and branching fraction

  • Recksiegel and Sumino, Phys. Lett. B 578, 369 (2004) [hep-ph/0305178]

  • Kniehl et al., PRL 92 242001 (2004) [hep-ph/0312086]

  • Godfrey and Isgur, PRD 32, 189 (1985)

  • Fulcher, PRD 44, 2079 (1991)

  • Eichten and Quigg, PRD 49, 5845 (1994) [hep-ph/9402210]

  • Gupta and Johnson, PRD 53, 312 (1996) [hep-ph/9511267]

  • Ebert et al., PRD 67, 014027 (2003) [hep-ph/0210381]

  • Zeng et al., PRD 52, 5229 (1995) [hep-ph/9412269]

e+e-→gISRY(1S) Calculations


Summary of h b measurements from y 3s l.jpg
SUMMARY OF the bb angular momentum in spectroscopic notation (L=S, P, D,…)hb MEASUREMENTS from Y(3S)

CLEO

arXiv: hep-ph/0412158


Slide36 l.jpg

Segmented array of 6580 Thallium-doped CsI crystals 16 to 17.5 radiation lengths deep (Rad. L. >1.85 cm)

energy & position resolution:

The ElectroMagneticCalorimeter

Designed to detect electromagnetic showers over the energy range from 20 MeV to 4GeV

  • Also used to:

  • detect KL’s

  • identify electrons

e+ (3.1 GeV)

e- (8.65 GeV)