Recent Results on e + e hadrons Cross Sections from SND and CMD-3 - PowerPoint PPT Presentation

Recent Results on e + e − → hadrons Cross Sections from SND and CMD-3 Detectors at VEPP-2000 collider Vladimir Golubev Budker Institute of Nuclear Physics, Novosibirsk, Russia 13-th International Workshop on Tau Lepton Physics (TAU2014) at RWTH Aachen University, September 14–19, 2014

VEPP-2000 Collider ILU CMD-3 3 MeV Linac VEPP-2000 B - 3M BEP 250 MeV synchro- e + ,e − betatron booster 825 MeV SND 2 m 2 m e − → e + converter Designed luminosity: Main parameters: L ~ 2 µ 10 31 cm − 2 s − 1 (2E=1.0 GeV) collision period 82ns � L ~ 10 32 cm − 2 s − 1 (2E=2.0 GeV) beam current 0.2 A � bunch length 3.3cm Achieved luminosity: � L ~ 5 µ 10 30 cm − 2 s − 1 (2E=1.0 GeV) perimeter 24.4 m � L ~ 2 µ 10 31 cm − 2 s − 1 (2E=2.0 GeV) Energy spread 0.7 MeV � b x > b z = 6.3cm � 16.09.2014 V.B.Golubev TAU2014, Aachen 2

Detectors for VEPP-2000 SND CMD-3 1 – vacuum chamber 6 – electromagnetic 2 – drift chamber calorimeter LXe 3 – electromagnetic 7 – electromagnetic 1 – beam pipe, 2 – tracking system, 3 – aerogel calorimeter BGO calorimeter CsI threshold Cherenkov counters , 4 – NaI(Tl) crystals, 5 4 – Z – chamber 8 – yoke – phototriodes, 6 – iron electromagnetic shower 5 – CMD SC solenoid 9 – VEPP-2000 solenoid absorber, 7–9 – muon detector, 10 – VEPP-2000 focusing SC solenoids. 16.09.2014 V.B.Golubev TAU2014, Aachen 3

Collected Integrated Luminosities Experiments 2010 − 2012 √ s > 1.88 GeV Experiment/ year Integrated (1.05 − 2.0 GeV) luminosity 5 pb -1 0.07 pb -1 2010 25 pb -1 3.8 pb -1 2011 2012 17 pb -1 4.9 pb -1 47pb -1 8.8 pb -1 Total Experiment 2013 ρ - ω η′ η′ - meson ϕ - meson Energy region Integrated non- ( √ s, GeV) luminosity, region, region, pb -1 region, pb -1 resonant, pb -1 pb -1 pb -1 0.32 − 1.06 25 8.8 2.7 6.9 6.6 16.09.2014 V.B.Golubev TAU2014, Aachen 4

List of Processes e + e – → ηγ → 7 γ 1. e + e − → π + π − 2. e + e − → K + K − 3. e + e − → K + K − π + π − 4. e + e - → π + π − π + π − 5. e + e - → π + π − π + π − π + π − 6. e + e − → π + π − π + π - π 0 π 0 7. e + e − → π + π - π 0 8. e + e − → π + π − η 9. e + e − → π + π - π 0 η 10. e + e − → η '(958) 11. e + e − → p anti-p 12. e + e − → n anti-n 13. 16.09.2014 V.B.Golubev TAU2014, Aachen 5

e + e − → hg → 7 g (32pb − 1 ) It is first observation of radiative decays of ρ (1450) and φ (1680) mesons ρ (1450) φ (1680) Sum of ρ (770), ω (782), φ (1020) and ρ (1450) и φ (1680) with interference About 30 events ηγ ηγ above 1.15 GeV, are explained by ρ (1450) and φ (1680) decays. Peak cross sections are much larger of theoretical predictions from quark model: about 15 pb for ρ (1450) and about 10 pb for φ (1680). ρ(770), ω(782) , φ(1020) arXiv:1312.7078 [hep-ex] Phys. Rev. D 90, 032002 16.09.2014 V.B.Golubev TAU2014, Aachen 6

e + e − → p + p − Preliminary • e/ µ / π separation using particles e/ µ / π 40 momentum separation • can measure using energy N( µµ )/N(ee) and deposition in 30 compare to QED calorimeter 20 10 0 10 16.09.2014 V.B.Golubev TAU2014, Aachen 7

e + e − → K + K − Complicated form of cross section is Preliminary connected with interference of all excited vector resonances of this energy region SND SND Kaons selection was done using aerogel Cherenkov counters SND SND 16.09.2014 V.B.Golubev TAU2014, Aachen 8

e + e − → K + K − p + p − Preliminary Κ/π separation K p by dEdX in DC BABAR CMD-3 Analysis is close to publication 16.09.2014 V.B.Golubev TAU2014, Aachen 9

e + e − → p + p − p + p − � clean selection of 4 and 3 charged pions � statistical errors are at the level of 1-2% per point Preliminary mass distributions: � systematical errors are under investigation Preliminary BABAR CMD-3 CMD-3 PbarP threshold • a 1 (1260) p dominance • other states ( r (770)f 0 (600), r (770)f 0 (980), etc.) are seen, but small. 16.09.2014 V.B.Golubev TAU2014, Aachen 10

e + e − → 6 p e + e − → 3 (π + π − ) BABAR BABAR o o e + e − → 2 (π + π − π 0 ) • • CMD-3 CMD-3 Published: P Published: P hys.Lett. B723 (2013) 82 hys.Lett. B723 (2013) 82 Preliminary Preliminary 16.09.2014 V.B.Golubev TAU2014, Aachen 11

e + e − → p + p − gg e + e − → π + π - η e + e − → π + π - π 0 Preliminary Preliminary √ s(MeV) ρ (770), ρ′ (1450), ρ ″ (1700) ω (783), ω ′ (1420), ω″ (1650) Systematic error: ~5% Only half of statistics Calculated using measured e + e − → hp + p − cross section energy dependence the t − → hp − p 0 n t branching fraction based on CVC hypothesis is equal to (0.180±0.048)%, which is compatible with PDG value (0.139±0.01)% 16.09.2014 V.B.Golubev TAU2014, Aachen 12

e + e − → p + p − p 0 h ( h → 2 g ) intermediate states ω η , φη φη , first measurement ɑ ρ are clearly seen ω ′′ (1650) ω (783) φ ′ (1680) φ (1020) Preliminary Preliminary 16.09.2014 V.B.Golubev TAU2014, Aachen 13

Search for the process e + e − → h '(958) → p + p − h → p + p − gg m( gg ), MeV/c 2 m( gg ), MeV/c 2 arXiv: 1409.1664 [hep-ex] e − Result: G ( h ‘ → e + e − ) < 2.4 µ 10 − 3 eV; B( h ‘ → e + e − )< 2.1 µ 10 − 7 at 90% C.L.. g These limits are 10 times lower compared to the previous measurement The G ( h ‘ → e + e − ) unitarity limit is > 7.4 µ 10 − 6 eV h ' g e + 16.09.2014 V.B.Golubev TAU2014, Aachen 14

Baryon cross sections   πα β 2 2 4 C 2 M Total cross section:   σ = 2 + 2 ( s ) | G ( s ) | N | G ( s ) | ,   M E 3 s s   where C is the Coulomb factor, G E and G M are the electric and magnetic form factors. πα πα Cross section is not zero at − For protons: ≈ − β C /( 1 e ) β threshold for neutrons: C=1 From the measured cross section, a combination of the squared form factors (G E ,G M ) can be extracted. Differential cross section: The ratio of the form factors |G E /G M | can be determined from the analysis of the polar-angle distribution. 16.09.2014 V.B.Golubev TAU2014, Aachen 15

Preliminary Preliminary Systematic error ~6% 16.09.2014 V.B.Golubev TAU2014, Aachen 16

(Angular distribution) cos θ |G E | 2 ↔ sin 2 θ |G M | 2 ↔ (1+cos 2 θ ) E beam =960-1000MeV, |G E /G M |= 1.64 ± 0.26 cos θ SND |G E /G M | Preliminary 16.09.2014 V.B.Golubev TAU2014, Aachen 17

Cross section Preliminary Effective form factor: 2 2 + τ G G / 2 s 2 = M E τ = F , + τ 2 1 1 / 2 4 m N A comparison of proton and neutron FFs σ aver = 0.8 ± 0.2 nb Preliminary Systematics: ~0.25 nb (~30%) 16.09.2014 V.B.Golubev TAU2014, Aachen 18

Conclusions 1. Since 2010 VEPP-2000 e+e- collider had accumulated ~70 pb -1 data with each SND and CMD-3 detectors in the energy range E=0.3 – 2 GeV. 2. Data analysis on meson and nucleon production is in progress. The already collected data promise higher statistical precision on cross sections than previous experiments. 3. First publications on data analysis appeared ( 6 π , ωπ 0 , η γ ) , many preliminary results are in preparation for publications. 4. After VEPP-2000 upgrade in 2015 the data taking runs will be resumed with the goal of ~1 fb -1 integrated luminosity. 16.09.2014 V.B.Golubev TAU2014, Aachen 19