NEWS FROM CMD-3, SND EXPERIMENTS AT VEPP2000 Evgeny Solodov on behalf of CMD-3 and SND collaborations Budker Institute of Nuclear Physics Novosibirsk State University June 2018
2 E. Solodov. CMD-3, SND Overview June 2018 VEPP-2000 (2010-2013) Beam energy by Compton backscattering CMD-3 ILU 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 Ec.m . During 2010-2013 the luminosity was limited by shortage of positrons
3 E. Solodov. CMD-3, SND Overview June 2018 Energy measurement Starting from 2012, energy is monitored continuously using Compton backscattering MeV
4 E. Solodov. CMD-3, SND Overview June 2018
5 E. Solodov. CMD-3, SND Overview June 2018 Detector CMD-3 General purpose magnetic detector With excellent tracking and calorimeter Mu LXe DC ZC TOF CsI BGO
6 E. Solodov. CMD-3, SND Overview June 2018 Detector SND 1 – vacuum chamber, 2 – tracking DC, 3 – aerogel n=1.13 , 1.05 4 – NaI(Tl) crystals, 5 – phototriodes, 6 – absorber, 7–9 – muon detector, 10 – SC solenoids High-resolution NaI calorimeter with excellent tracking and PID
7 E. Solodov. CMD-3, SND Overview June 2018 Collected luminosity in 2011-2013 CMD-3 data, average per run Luminosity, 1/cm 2 s Energy ramping Limited e + production Beam energy, 2E, MeV About 60 pb-1 collected per detector The luminosity was limited by a deficit of positrons and limited energy of the booster. The VEPP-2000 upgrade has started in 2013.
8 E. Solodov. CMD-3, SND Overview June 2018 VEPP-2000 upgrade (2013-2016) 250 m beamline VEPP-2000 New injection complex Collider upgrades: CMD-3 upgrades: • x10 more intense • New electronics for positron source Lxe calorimeter • booster up to 1 GeV • New TOF system (match VEPP-2000) • DAQ and electronics upgrades Detectors resumed data taking by the end of 2016
9 E. Solodov. CMD-3, SND Overview June 2018 2017-2018 data taking VEPP-2000 Luminosity 2017-2018 Now ! * * 2011-2013 CMD-3 data, average per CMD-3 data, average for 10% of best runs 10% best runs Beam energy, 2E, MeV Beam energy, 2E, MeV In 2017: big improvement in luminosity, still way to go. Above 1 GeV: ~50 pb -1 collected 4*10 31 at E = 550 MeV has been achieved! D0(2007)* 4 pb-1 Below 1 GeV – 2017-2018: and pp, nn threshold 14 pb-1 66 pb -1
10 E. Solodov. CMD-3, SND Overview June 2018 Overview of CMD-3 data taking runs 1.28-2.007 GeV Collected integral, 1/pb scan 𝜕 , 𝜚 1-2 GeV upgrade scan 0.55-1 GeV scan 0.36-1 GeV scan
11 E. Solodov. CMD-3, SND Overview June 2018 At VEPP2000 - we do exclusive measurements of e + e - -> hadrons and study production dynamics.
Luminosity determination Overall runs systematic uncertainty is about 1% Fit: (0.1 ± 0.2)% Fit: (2 ± 1)% scan up, 2012 scan up & down, 2011 Fit: (-0.3 ± 0.3)% Fit: (-0.25 ± 0.09)% ϕ→ω scan, 2013 scan 2017 12
13 June 2018 E. Solodov. CMD-3, SND Overview CMD-3 published results from 2011-2013 PLB 759 (2016) 634 PLB 760 (2016) 314 PLB 760 (2017) 314 PLB 768 (2017) 345 PLB 723 (2013) 82 PLB 756 (2016) 153 PLB 773 (2017) 150 Intermediate structures are studying in every final state
14 E. Solodov. CMD-3, SND Overview June 2018 Correction to K + K - at φ • We observe large discrepancy between CMD-2(2008) CMD-2 and CMD-3 data. CMD-2(2017) • CMD-2 has trigger DC+Z- CMD-3(2017) chamber+CsI calorimeter energy deposition – no cross check! Kaons stop in first wall and only decays and interactions provide trigger. • CMD-3 has only DC hits in trigger, but all information from Z-chamber(the same!) and calorimeter. • We can directly measure Trigger estimate by trigger efficiency of CMD-2. MC CMD-2 (2008) • Corrected data should be Direct measurement published soon by CMD-3 (2017) Trigger correction (1+ δ ) trig = 1.094±0.040 ( сист .) Cross check for Bhabha events ε trig = 0.9949±0.0001
15 E. Solodov. CMD-3, SND Overview June 2018 Dominant channel e + e - -> π + π - 2013 data CMD-3 preliminary Source Goal Current estimation 9.4 pb -1 e/ π /µ separation Radiative 0.2% 0.2% (cross-section) ● by momentum Correction 0.0-0.4% (mom.sep.) Δ by energy deposition Event separation 0.2% 0.1-0.5% (mom. sep.) ~1.5% (energy sep.) Fiducial volume 0.1% ok Beam energy 0.1% ok Pion corrections 0.1% 0.1% -nucl. int. (decay, nucl.int.) 0.6-0.3% decays at low energies Combined 0.33% 0.4-0.9% (mom.sep.) 1.5% (energy sep.) Some corrections are not applied (result is still “blinded”) Hope to finalize it later this year
16 E. Solodov. CMD-3, SND Overview June 2018
E. Solodov. CMD-3, SND Overview June 2018 17 More preliminary CMD-3 results e + e - -> Κ + Κ - π 0 e + e - -> K S K L e + e - -> 2( π + π - ) BaBar BaBar CMD-3 CMD-3 Br( ω → π 0 e + e - ) Experiment events data, Analysis in progress pb -1 Publications are in -4 CMD-2 (8.19±0,71±0.62) ∗ 10 230 3.3 preparations -4 SND (7.61±0,53±0.64) ∗ 10 613 9.8 -4 CMD-3 (6.90±0.33) ∗ 10 1169 8
E. Solodov. CMD-3, SND Overview June 2018 18 NEW! e + e - -> 3( π + π - ) π 0 Based on 56 pb -1 in 1600-2000 MeV BaBar CMD-3 Dominated by ω 4 π η 4 π Publications are in preparations
19 E. Solodov. CMD-3, SND Overview June 2018 SND@VEPP-2000 summary of results , (journal articles) Published: Published, cont’d : 1. e+e- � π 0 π 0 γ , Ph.Rev.D, (2013,2016) 8. e+e- � η , JETP Lett.,(2015) 2. e+e- � nn, Phys.Rev.D,(2014) 9. e+e- � K + K - , Phys.Rev.D,(2016) 3. e+e- � NN-6 π , JETP Lett.,(2014) 10. e+e- � ωηπ 0 , Phys.Rev.D,(2016) 4. e+e- � ηγ , Phys.Rev.D,(2014) 11. e+e- � ωη , Phys.Rev.D,(2016) 5. e+e- � η / , Phys.Rev.D,(2015) 12. e+e- � π 0 γ , Phys.Rev.D,(2016) 6. e+e- � ηπ + π - , Phys.Rev.D,(2015) 13. e+e- � NN-n π , Phys.At.Nucl, (2017) 7. e+e- � π + π - π 0 , JETP,(2015) In print: In analysis: 1. e+e- � π + π - , 1. e+e- � K S K L π 0 , Phys.Rev.D, 2. e+e- � ηπ + π - , Phys.Rev.D, 2. e+e- � ηπ 0 π + π - , 3. e+e- � π + π - π 0 π 0 , 3. e+e- � η K + K - , JETP, 4. e+e- � K + K - π 0 , 5. e+e- � ωπ 0 π 0 , 6. e+e- � 6 π
20 E. Solodov. CMD-3, SND Overview June 2018 Some SND results overview e+e - →π + π - π 0 e+ e - →π + π - η e+ e - →Κ + Κ - η J.Exp.Theor.Phys. 121 (2015) 1. Phys. Rev. D 91, 052013 (2015) Phys.Rev.D,(2016) Phys.Rev.D,(2014)
21 E. Solodov. CMD-3, SND Overview June 2018 e + e - → ωπ 0 η , Phys. Rev. D 94,032010 (2016) 7 photon final state a 0 dominance Cross section: e + e - → π 0 π 0 ηγ → 7 γ ωπ 0 η ~ 5% of hadr. cross sect. phase at 1.8-2.0 GeV ω space e + e - →ωπ 0 η ω a 0 π 0 γ mass ηπ 0 mass � First measurement of the e + e - → ωπ 0 η cross section. � The dominant mechanism is ω a 0 (980). � The cross section is about 2.5 nb, 5% of the total hadronic cross section Intermediate structures are studying in every final state
22 E. Solodov. CMD-3, SND Overview June 2018 e + e - -> π + π - SND (preliminary) ― SND errors SND (preliminary) (stat ⊕ syst)
23 E. Solodov. CMD-3, SND Overview June 2018 2017: e + e - -> pp at NN threshold In 2017 CMD-3 and SND has performed the scan at the NNbar threshold with a step smaller than c.m. machine energy spread (1.2 MeV). The e+e- -> ppbar cross section demonstrate exponentially fast rising in about 1 MeV interval. ), nb 2 p BaBar p → CMD-3 1.5 - e CMD-3 (2017) + (e σ 1 0.5 0 1850 1900 1950 2000 Ec.m., MeV
24 E. Solodov. CMD-3, SND Overview June 2018 CMD-3 has confirmed fast drop of the cross section, and new scan shows the scale of the drop consistent with ppbar cross section rise ~1 MeV. BaBar CMD-3 CMD-3 (2017)
25 E. Solodov. CMD-3, SND Overview June 2018 No indication of NNbar threshold in the e + e - - > 2( π + π - ) reaction! BaBar CMD-3 We continue search for the NNbar threshold indication in other multi-hadron reactions
26 NEW! Structure in e + e - -> K + K - π + π - BaBar data CMD-3 2017 data One more channel, where NN threshold structure has been observed!
27 Milstein-Salnikov prediction (fit?) Theoretical calculation well describes the experimental data for ppbar production in e+e- Using predicted shape convoluted with radiative effects and beam energy spread we fit visible XS: Good agreement in shape – theoretical prediction should be increased by 10% to fit our 2017 data Note NON-ZERO XS at the threshold.
28 16.06.18 E.Soodov VEPP2000 at NNbar Milstein-Salnikov prediction (fit?) Theoretical calculation not so well describes the experimental data for nnbar production in e+e-, but not in contradiction. , nb 1.4 DM2 n n SND → 1.2 We are eagerly wait for the result of - e + (e 1 nnbar analysis from SND and CMD-3 σ at the threshold 0.8 0.6 Should be later this year. 0.4 0.2 0 1880 1900 1920 1940 1960 1980 2000 E , GeV c.m.
29 E. Solodov. CMD-3, SND Overview June 2018 e+e- -> nn SND (preliminary) ● exp ○ SND 2011-2012 sim ● SND 2017 𝑜𝑜 The difference: -- incorrect 𝑜𝑜 simulation -- beam background cosm -- cosmic background e+e- Systematic uncertainty ~20%, mainly due to MC
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