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 Circumference 366 m VEPP-3 Beam energy 1 ÷ 6 GeV VEPP-4M Number of bunches 2 × 2 Luminosity, E =1 . 5 GeV 2 × 10 30 cm − 2 s − 1 Luminosity, E =5 . 0 GeV 2 × 10 31 cm − 2 s − 1 KEDR • 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 ��� ��� TS4 ��� ��� TS3 ��� ��� ��� ��� ��� ��� ��� ��� VEPP−4M electron beam KEDR TS1 ��� ��� ��� ��� TS2 ��� ��� ��� ��� ��� ��� ��� ��� HPGe detector Compton photons LM Cryostat KEDR GEM Select 50 laser beam CO2 laser S.Eidelman, BINP p.3/21
HADRON11, Munich June 13-17, 2011 VEPP-4M Energy Behaviour VEPP-4M energy, MeV RDM measurements CBS measurements 1777.65 interpolated energy 1777.6 1777.55 1777.5 1777.45 1777.4 1777.35 1777.3 1777.25 1777.2 1777.15 06/04 07/04 08/04 09/04 10/04 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 σ obs , nb σ obs , nb σ obs , nb σ obs , nb 1200 σ obs , nb Scan IV : 2500 σ W = 0.664 1000 ± 0.018 Scans I,II σ W = 0.839 σ W = 0.698 ± 0.002 2000 ± 0.013 800 1500 600 Scan III : σ W = 0.900 400 ± 0.020 1000 200 500 0 1546 1547 1548 1549 1550 1551 0 1544 1546 1548 1550 1552 1554 E, MeV E, MeV E, MeV E, MeV E, MeV M J/ψ = (3096 . 913 ± 0 . 006 ± 0 . 009) MeV M ψ ′ = (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 KEDR 2003-2005 5 KEDR 2003-2006 4 KEDR 2003 4 KEDR 2003 3 E760 1993 E760 1993 (using M ψ (2s) by KEDR) 3 (using M ψ by KEDR) 2 SPEC 1987 2 OLYA 1980 OLYA 1980 1 1 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 M Ι/ψ - 3097 M ψ (2s) - 3686 S.Eidelman, BINP p.8/21
HADRON11, Munich June 13-17, 2011 Measurement of Γ ee · B ( ψ ′ → hadrons ) for ψ ′ – I σ [nb] scan 1, σ W = 1 . 08 MeV 800 scan 2, σ W = 1 . 05 MeV 700 scan 3, σ W = 0 . 98 MeV 600 500 400 300 200 100 3675 3680 3685 3690 3695 W[MeV] S.Eidelman, BINP p.9/21
HADRON11, Munich June 13-17, 2011 Measurement of Γ ee · 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 Γ ee · B ( ψ ′ → hadrons ) for ψ ′ – III • Γ e + 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 B h Γ e + e − = (2 . 294 ± 0 . 015 ± 0 . 037) keV, about 3 times better than the best previous one. • Using the world-average values of Γ e + e − and B h 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 Γ ee · B ( ψ ′ → hadrons ) for ψ ′ – IV KEDR 2011 Γ ee × B hadrons ψ (2 S ) BES2 2008 BES2 2006 KEDR BES2 2002 Υ rev. 1989 MRK I 1975 DASP 1979 MRK1 1975 1.8 2 2.2 2.4 2.6 1.8 2 2.2 2.4 2.6 keV Γ ee ( ψ (2 S )) , keV S.Eidelman, BINP p.12/21
HADRON11, Munich June 13-17, 2011 Measurement of Γ ee · B ( ψ ′ → hadrons ) for ψ ′ – V KEDR 2011 BES2 2008 E835 2007 BES2 2006 BES2 2002 E760 1993 200 250 300 350 400 Γ ( ψ (2 S )) , keV S.Eidelman, BINP p.13/21
HADRON11, Munich June 13-17, 2011 Determination of ψ (3770) Parameters – I σ , [nb] scan 1 10 scan 2 scan 3 8 VDM 6 F ( q ) ∝ e − q 2 a 2 No Interference 4 2 3740 3760 3780 3800 3820 3840 3860 3880 W,[MeV] D ∝ | A ψ (3770) + A ψ ′ e iφ + B e iφ | 2 σ D ¯ D ∝ | A ψ (3770) + B n . r . F e iφ | 2 σ D ¯ S.Eidelman, BINP p.14/21
HADRON11, Munich June 13-17, 2011 Determination of ψ (3770) Parameters – III M ,[MeV/ c 2 ] Model,F(q) 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 − q 2 3780 . 5 ± 2 . 3 28 . 2 ± 4 . 5 15 . 3 a 2 constant 3778 . 1 ± 1 . 5 30 . 4 ± 3 . 9 13 . 7 1 3779 . 3 ± 1 . 7 25 . 1 ± 4 . 4 17 . 2 1+ aq 2 + bq 4 1 3779 . 0 ± 1 . 7 24 . 4 ± 3 . 7 17 . 7 1+ aq b 1 3780 . 0 ± 1 . 9 25 . 3 ± 4 . 7 17 . 6 ( W − M ψ ′ ) a 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 +0 . 3 +5 . 7 σ NR shape − 1 . 6 − 0 . 5 R 0 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 – ≈ +0 . 5 ≈ +5 . 7 Total − 1 . 7 − 0 . 7 KEDR: M ψ (3770) = (3779 . 3 ± 1 . 7 +0 . 5 Γ ψ (3770) = (24 . 9 ± 4 . 3 +5 . 7 − 1 . 7 ) MeV , − 0 . 7 ) MeV PDG: M ψ (3770) = (3772 . 92 ± 0 . 35) MeV , Γ ψ (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 Γ e + 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 L dt ≈ 300 nb − 1 was collected � in a scan with a step ≈ 2 σ W (1.4-1.9 MeV) σ E (MeV) 0.7 0.6 0.5 0.4 1000 1100 1200 1300 1400 1500 E (MeV) S.Eidelman, BINP p.19/21
HADRON11, Munich June 13-17, 2011 Search for Narrow Resonances – III • The model: a resonance with M R , Γ R ee on top of a flat BG • The fits use the range M R ± 13 MeV • M R is varied in 0.1 MeV steps • A systematic error of ∼ 50% conservatively • Γ R ee · B ( R → hadrons ) < 120 eV, 4-5 times more stringent than at ADONE in 1975-1978: γγ 2, 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 (2 S ) measured. The accuracy reaches (3 − 5) · 10 − 6 • New precise value of Γ e + 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 Γ e + 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
Recommend
More recommend
