Recent Results from the KEDR Detector Simon Eidelman Budker - - PowerPoint PPT Presentation

HADRON11, Munich June 13-17, 2011

Recent Results from the KEDR Detector

Simon Eidelman

Budker Institute of Nuclear Physics, Novosibirsk, Russia

Outline

• 1. J/ψ and ψ′ masses
• 2. Parameters of ψ′
• 3. Parameters of ψ(3770)
• 4. Search for narrow resonances
• 5. Conclusions

S.Eidelman, BINP p.1/21

HADRON11, Munich June 13-17, 2011

VEPP–4M collider

KEDR

VEPP-4M

VEPP-3

Circumference 366 m Beam energy 1÷6 GeV Number of bunches 2 × 2 Luminosity, E =1.5 GeV 2 × 1030 cm−2s−1 Luminosity, E =5.0 GeV 2 × 1031 cm−2s−1

• Resonant depolarization technique:

Instantaneous measurement accuracy ≃ 1 × 10−6 Energy interpolation accuracy (5 ÷ 15) × 10−6 (10 ÷ 30 keV)

• Infrared light Compton backscattering:

Statistical accuracy ≃ 5 × 10−5 / 30 minutes Systematic uncertainty ≃ 3 × 10−5 (50 ÷ 70 keV) S.Eidelman, BINP p.2/21

HADRON11, Munich June 13-17, 2011

Compton Backscattering Monitor

Realized at BESSY-I in 1987

Cryostat HPGe detector GEM Select 50 CO2 laser TS1 TS4 TS3 TS2 LM laser beam Compton photons VEPP−4M electron beam

• KEDR

KEDR S.Eidelman, BINP p.3/21

HADRON11, Munich June 13-17, 2011

VEPP-4M Energy Behaviour

06/04 07/04 08/04 09/04 10/04 1777.15 1777.2 1777.25 1777.3 1777.35 1777.4 1777.45 1777.5 1777.55 1777.6 1777.65

VEPP-4M energy, MeV RDM measurements CBS measurements interpolated energy

During the run, E measured by CBS and from interpolation

S.Eidelman, BINP p.4/21

HADRON11, Munich June 13-17, 2011

KEDR detector

• 1. Vacuum chamber
• 2. Vertex detector
• 3. Drift chamber
• 4. Threshold aerogel counters
• 5. ToF counters
• 6. Liquid krypton calorimeter
• 7. Superconducting coil
• 8. Magnet yoke
• 9. Muon tubes
• 10. CsI calorimeter
• 11. Compensating s/c solenoid

S.Eidelman, BINP p.5/21

HADRON11, Munich June 13-17, 2011

J/ψ and ψ′ Mass Measurement – I

E, MeV σobs, nb E, MeV σobs, nb E, MeV σobs, nb E, MeV σobs, nb

Scans I,II σW = 0.839 ± 0.013 Scan III: σW = 0.900 ± 0.020 Scan IV: σW = 0.664 ± 0.018

200 400 600 800 1000 1200 1546 1547 1548 1549 1550 1551

E, MeV σobs, nb σW = 0.698±0.002 500 1000 1500 2000 2500 1544 1546 1548 1550 1552 1554

MJ/ψ = (3096.913 ± 0.006 ± 0.009) MeV Mψ′ = (3686.126 ± 0.007 ± 0.011) MeV

S.Eidelman, BINP p.6/21

HADRON11, Munich June 13-17, 2011

J/ψ and ψ′ Mass Measurement – II

• Systematic errors in mass measurements are the main issue
• More than 20 different effects considered
• Energy spread, energy assignment, energy difference of e+ and e−,

beam misalignment, luminosity etc.

• No significant improvement for the J/ψ

because the additional scan had bigger systematics

S.Eidelman, BINP p.7/21

HADRON11, Munich June 13-17, 2011

J/ψ and ψ′ Mass Measurement – III

MΙ/ψ - 3097 KEDR 2003-2005 KEDR 2003 OLYA 1980 E760 1993 (using Mψ(2s) by KEDR) SPEC 1987

1 2 3 4 5

• 0.4
• 0.3
• 0.2
• 0.1

0.1 0.2 0.3

Mψ(2s) - 3686 KEDR 2003-2006 KEDR 2003 OLYA 1980 E760 1993 (using Mψ by KEDR)

1 2 3 4

• 0.2
• 0.15
• 0.1
• 0.05

0.05 0.1 0.15

S.Eidelman, BINP p.8/21

HADRON11, Munich June 13-17, 2011

Measurement of Γee · B(ψ′ → hadrons) for ψ′ – I

3675 3680 3685 3690 3695 100 200 300 400 500 600 700 800

σ [nb] W[MeV]

scan 1,σW = 1.08 MeV scan 2,σW = 1.05 MeV scan 3,σW = 0.98 MeV

S.Eidelman, BINP p.9/21

HADRON11, Munich June 13-17, 2011

Measurement of Γee · B(ψ′ → hadrons) for ψ′ – II

Source Scan 1 Scan 2 Scan 3 Common 1-2 Common Lumin. 1.6 1.7 1.2 1.6 0.4 MC gener. 0.9 0.9 1.1 0.9 0.9 Trigger 0.6 0.6 0.3 0.6 0.3 Selection 0.5 0.3 0.6 0.3 0.3 MC nucl. 0.3 0.3 0.3 0.3 0.3 Energy 0.15 0.18 0.60 0.15 0.15 MC vert. det. 0.10 0.17 0.10 0.10 0.10 Fit 0.2 0.2 0.2 0.2 0.2 Total 2.0 2.1 1.9 2.0 1.1 S.Eidelman, BINP p.10/21

HADRON11, Munich June 13-17, 2011

Measurement of Γee · B(ψ′ → hadrons) for ψ′ – III

• Γe+e− · B(ψ′ → h) = (2.245 ± 0.015 ± 0.036) keV,

much more precise than the only previous direct measurement

• Using the world-average value of Bh

Γe+e− = (2.294 ± 0.015 ± 0.037) keV, about 3 times better than the best previous one.

• Using the world-average values of Γe+e− and Bh

Γ = (297 ± 2 ± 8) keV, again about 3 times better than the best previous one.

S.Eidelman, BINP p.11/21

HADRON11, Munich June 13-17, 2011

Measurement of Γee · B(ψ′ → hadrons) for ψ′ – IV

1.8 2 2.2 2.4 2.6

KEDR MRK I 1975 Γee × Bhadrons ψ(2S) keV

1.8 2 2.2 2.4 2.6

KEDR 2011 BES2 2008 BES2 2006 BES2 2002 Υ rev. 1989 DASP 1979 MRK1 1975 Γee (ψ(2S)), keV

S.Eidelman, BINP p.12/21

HADRON11, Munich June 13-17, 2011

Measurement of Γee · B(ψ′ → hadrons) for ψ′ – V

200 250 300 350 400

KEDR 2011 BES2 2008 E835 2007 BES2 2006 BES2 2002 E760 1993 Γ (ψ(2S)), keV

S.Eidelman, BINP p.13/21

HADRON11, Munich June 13-17, 2011

Determination of ψ(3770) Parameters – I

3740 3760 3780 3800 3820 3840 3860 3880 2 4 6 8 10

σ, [nb] W,[MeV] scan 1 scan 2 scan 3 VDM F(q) ∝ e− q2

a2

No Interference σD ¯

D ∝ |Aψ(3770) + Aψ′ eiφ + B eiφ|2

σD ¯

D ∝ |Aψ(3770) + Bn.r. F eiφ|2

S.Eidelman, BINP p.14/21

HADRON11, Munich June 13-17, 2011

Determination of ψ(3770) Parameters – III

Model,F(q) M,[MeV/c2] Γ,[MeV] C.L. ,[%] VDM(ψ′) 3779.7 ± 1.7 24.9 ± 4.3 18.5 No Interf. 3773.2 ± 0.5 23.9 ± 2.3 2.5 e− q2

a2

3780.5 ± 2.3 28.2 ± 4.5 15.3 constant 3778.1 ± 1.5 30.4 ± 3.9 13.7

1 1+aq2+bq4

3779.3 ± 1.7 25.1 ± 4.4 17.2

1 1+aqb

3779.0 ± 1.7 24.4 ± 3.7 17.7

1 (W −Mψ′ )a

3780.0 ± 1.9 25.3 ± 4.7 17.6 VDM (ψ(4039)) 3778.2 ± 1.6 30.6 ± 3.9 12.2 S.Eidelman, BINP p.15/21

HADRON11, Munich June 13-17, 2011

Determination of ψ(3770) Parameters – IV

Source Mass, MeV Width, MeV σNR shape

+0.3 −1.6 +5.7 −0.5

R0 variation 0.3 0.3 Event selection 0.3 0.3 Luminosity 0.1 0.1 Detection efficiency 0.1 0.1 Energy assignment 0.03 – Total ≈ +0.5

−1.7

≈ +5.7

−0.7

KEDR: Mψ(3770) = (3779.3 ± 1.7+0.5

−1.7) MeV,

Γψ(3770) = (24.9 ± 4.3+5.7

−0.7) MeV

PDG: Mψ(3770) = (3772.92 ± 0.35) MeV, Γψ(3770) = (27.3 ± 1.0) MeV

S.Eidelman, BINP p.16/21

HADRON11, Munich June 13-17, 2011

Determination of ψ(3770) Parameters – V

A few general conclusions:

• Mass is higher than in previous measurements, but

agrees with BaBar that also took into account interference

• Width is in reasonable agreement with previous measurements
• With our data sample we do not observe any shape anomaly
• Absolutely mandatory to take into account interference:
• There are usually two solutions with the same mass, width and likelihood,

but strongly differing (a factor of up to 3) leptonic width

• While the current world-average value is Γe+e− = 259 ± 16 eV,

with interference effects included it is higher and might be (400-500) eV

S.Eidelman, BINP p.17/21

HADRON11, Munich June 13-17, 2011

Search for Narrow Resonances – I

KEDR scanned the c.m.energy range from 1.85 to 3.1 GeV searching for narrow resonances

W (MeV) W (MeV) W (MeV)

S.Eidelman, BINP p.18/21

HADRON11, Munich June 13-17, 2011

Search for Narrow Resonances – II

• Ldt ≈ 300 nb−1 was collected

in a scan with a step ≈ 2σW (1.4-1.9 MeV)

E (MeV) σE (MeV) 0.4 0.5 0.6 0.7 1000 1100 1200 1300 1400 1500

S.Eidelman, BINP p.19/21

HADRON11, Munich June 13-17, 2011

Search for Narrow Resonances – III

• The model: a resonance with MR, ΓR

ee on top of a flat BG

• The fits use the range MR ± 13 MeV
• MR is varied in 0.1 MeV steps
• A systematic error of ∼ 50% conservatively
• ΓR

ee · B(R → hadrons) < 120 eV,

4-5 times more stringent than at ADONE in 1975-1978: γγ2, B ¯ B and BOSON groups scanned 1.42-3.1 GeV

• KEDR hopes to measure R in this W range to 5%

S.Eidelman, BINP p.20/21

HADRON11, Munich June 13-17, 2011

Conclusions

• Masses of J/ψ and ψ(2S) measured. The accuracy reaches (3 − 5) · 10−6
• New precise value of Γe+e− · B(ψ′) significantly improves

the values of both leptonic and total width for ψ′

• Interference effects are important for M and Γ of ψ(3770)
• Multiple solutions make difficult Γe+e− determination for ψ(3770)
• No narrow states found between 1.85 GeV and J/ψ
• New R measurements are planned between 2 and 11 GeV

S.Eidelman, BINP p.21/21