Hadronic Cross Section Measurements at Belle and perspectives at - PowerPoint PPT Presentation

Hadronic Cross Section Measurements at Belle and perspectives at BELLE-II Boris Shwartz, BINP, Novosibirsk Budker Institute of Nuclear Physics, Novosibirsk State University, Novosibisrsk, Russia PhiPsi 2017, Mainz 26.06.2017 1

Belle Detector The primary goal of the Belle and BaBar Aerogel Cherenkov cnt. SC solenoid n=1.015~1.030 experiments was to discover 1.5T the CP violation in B 3.5 GeV e + CsI(Tl) mesons and to measure the 16 X 0 parameters of CPV. This TOF counter was achieved by both 8 GeV e − experiments in 2001 C entral D rift C hamber small cell +He/C 2 H 6 Peak lumi record at KEKB: L=2.1 x 10 34 /cm2/sec with Si vtx. det. μ / K L detection crab cavities 3/4 lyr. DSSD 14/15 lyr. RPC+Fe E − = 8 GeV, E + = 3.5 GeV, √ s=10.58 GeV, βγ =0.42 2010 F/B asymmetric detector ∫ − = 1 Ldt 1 ab High vertex resolution, magnetic spectrometry, 1999 excellent calorimetry and sophisticated particle ID ability PhiPsi 2017, Mainz 26.06.2017 2

Other important results • Observation of direct CP violation in B decays • Measurements of the CPV parameters in different modes ( φ K 0 , η′ K 0 , K S K S K S , …) • Measurements of rare decay modes (e.g., B � τν , D τν ) • Observation of new charmonium-like and bottomonium-like hadronic states • b � s transitions: probe for new sources of CPV and constraints from the b � s γ branching fraction • Forward-backward asymmetry (A FB ) in b � sl + l - has become a powerful tool to search for physics beyond SM. • Observation of D mixing • Search for lepton flavour violation in τ decays • Study of the hadronic τ decays • Precise measurement of the hadronic cross sections in γγ and e + e − ( γ ISR ) processes So wide research area became possible because of clean event environment and well defined initial state in the e + e − experiments as PhiPsi 2017, Mainz 26.06.2017 3 well as high luminosity and general-purpose detectors

R(s) measurements at Belle PDG ISR: with γ ISR detection, full reconstruction ISR: mostly without γ ISR detection Direct e + e − scan PhiPsi 2017, Mainz 26.06.2017 4

R b : Data and Fit PRD 93, 011101(R) (2016) = ± + 0.6 2 M (10891.1 3.2 ) MeV/c 10860 - 1.7 Γ = + + (53.7 7.1 1.3 ) MeV 10860 - 5.6 - 5.4 = + + 6.4 9 2 M ( 10987 . 5 ) MeV/c − 11020 - 2 . 5 2 . 1 Γ = + + 9 2 (61 ) MeV − 11020 19 - 20 φ φ = ± + 1.4 ( 11020) - ( 10860) (-1.0 0.4 ) rad. - 0.1 PhiPsi 2017, Mainz 26.06.2017 5

Contribution of exclusive cross sections to the total cross section DD DD* D*D* DD* π DD π σ (e + e − → D (*) D * ) Phys. Rev.Lett. 98, 092001 (2007) e + e − → D 0 D – π + Phys.Rev.Lett.100,062001(2008) e + e − → D s (*)D s (*) D s D s +D s D s *+D s *D s * Λ c Λ c Phys.Rev.D 83, 011101 (2011) e + e – →Λ c + Λ c – Phys.Rev.Lett. 101,172001(2008) Results on XYZ states will be presented by R.Mizuk PhiPsi 2017, Mainz 26.06.2017 6

Contribution of exclusive cross sections to the total cross section BES: R tot – R uds ; Belle : ∑ R excl Results on XYZ states will be presented by R.Mizuk PhiPsi 2017, Mainz 26.06.2017 7

e + e − → φ π + π − and e + e − → f 0 (980) π + π − PRD 80, 031101 (2009) 673 fb -1 M ( φ (1680)) = (1689 ± 7 ± 10) MeV/c 2 , Γ ( φ (1680)) = (211 ± 14 ± 19) MeV/c 2 Cross section Syst. Errors - 8.6% M (Y(2175)) = (1689 ± 7 ± 10) MeV/c 2 , and 6.9% Γ (Y(2175)) = (211 ± 14 ± 19) MeV/c 2 PhiPsi 2017, Mainz 26.06.2017 8

Published ISR results at Belle PhiPsi 2017, Mainz 26.06.2017 9

Why do we need low energy hadronic cross section? Past and future of muon (g – 2) experiments Fred Jegerlehner, arXiv:1705.00263v1 [hep-ph] 30 Apr 2017 PhiPsi 2017, Mainz 26.06.2017 10

Fred Jegerlehner, arXiv:1705.00263v1 [hep-ph] 30 Apr 2017 PhiPsi 2017, Mainz 26.06.2017 11

Contributions of various final states to hadronic vacuum polarization (HVP) term of a m PhiPsi 2017, Mainz 26.06.2017 12

ISR measurements at BABAR PhiPsi 2017, Mainz 26.06.2017 13

Data from BES III (Tau 2016) Yaqian WANG, Tau-2016 PhiPsi 2017, Mainz 26.06.2017 14

Belle: low mass ISR study 526.6 fb -1 (preliminary, suspended?) Belle systematic error goal is 5% But difficult to achieve. Main problems: Improper trigger Lack of manpower: 2-3 people only vs ~20 at BaBar PhiPsi 2017, Mainz 26.06.2017 15

KEKB σ x ~100 μ m, σ y ~2 μ m Nano-Beam SuperKEKB σ x ~10 μ m, σ y ~60nm PhiPsi 2017, Mainz 26.06.2017 16

All details are in the Belle II Detector EM Calorimeter: Changzheng YUAN CsI(Tl), waveform sampling talk electronics (barrel) Pure CsI + waveform KL and muon detector: sampling (end-caps) later Resistive Plate Counter (barrel outer layers) electrons (7GeV) Scintillator + WLSF + MPPC (end-caps , inner 2 Central Drift Chamber barrel layers) Smaller cell size, long lever arm positrons (4GeV) Vertex Detector 2 layers Si Pixels (DEPFET) + 4 layers Si double sided strip Particle Identification DSSD Time-of-Propagation + New software, improved tracking, ... counter (barrel) + Optimization for low multiplicity trigger Prox. focusing Aerogel + Improved simulation, generators and RICH (forward) GRID PhiPsi 2017, Mainz 26.06.2017 17

Expected Luminosity Integrated luminosity ab -1 peak luminosity, cm -2 s -1 Calendar Year PhiPsi 2017, Mainz 26.06.2017 18

ISR at Belle II vs. BESIII Chengping Shen, Photon 2017 ISR produces events at all CM energies BESIII can reach With > 5(10) ab -1 data sample, ISR e+e- a charmonium+light hadrons: π + π -J/ Ψ , π + π - Ψ (2S), K+K-J/ Ψ , K+K- Ψ (2S), γ X(3872), π + π -X(3872), π + π -hc, π + π -hc(2P), ω XcJ, φ XcJ, η J/ Ψ , η ’J/ Ψ , η Ψ (2S), η hc]; and charm meson pair+light hadrons [DD, DD*, DD* π , . . . PhiPsi 2017, Mainz 26.06.2017 19

Potential of ISR for low energy range ⎧ ⎫ + 4 dl 2 α m s m s = − (ln 1 ) ⎨ ⎬ − 2 2 Ldm π s s ( s m ) m ⎩ ⎭ e KEKB VEPP- BEPC-II 2000 8 ⋅ 10 35 Luminosity, 10 32 10 33 см -2 s -1 Integrated lum. 8000 fb -1 1 fb -1 10 fb -1 (per 10 7 s) Integrated in the 8 fb -1 1 fb -1 range [1-2] GeV (~0.8 @ cos θ <0.7) Integrated in the 20 fb -1 10 fb -1 range [2-3] GeV (~2 @ cos θ <0.7) PhiPsi 2017, Mainz 26.06.2017 20

Improvements at Belle II relevant to low mass ISR Trigger Belle Belle II Bhabha in CM frame γ Hadr. Using the Bhabha topology, sum back to back TCs Energy . 1. Improved Bhabha veto logic for Belle II 2. Several independent trigger modes are invented to monitor and check the trigger efficiencies PhiPsi 2017, Mainz 26.06.2017 21

Improvements at Belle II relevant to low-mass ISR Central Drift Chamber Belle longer lever arm Improved momentum resolution and dE/dx Belle II normal cell small cell 18 mm 10 mm 6~8 mm 10~20 mm Belle Belle II inner most sense wire r=88mm r=168mm outer most sense wire r=863mm r=1111.4mm Number of layers 50 56 Better momentum resolution – Total sense wires 8400 14336 better invariant mass resolution Gas He:C 2 H 6 He:C 2 H 6 sense wire W( Φ 30 μ m) W( Φ 30 μ m) field wire Al( Φ 120 μ m) Al( Φ 120 μ m) PhiPsi 2017, Mainz 26.06.2017 22

Systematic uncertainties of BaBar measurements ( PRD 86, 032013 (2012)) In general higher Can we improve systematics at Belle II? statistics provides To try to do that we need to: more possibilities • Continuously and carefully monitor the trigger efficiency, track and to study photon reconstruction efficiency and PID (mostly m/p) efficiency systematics • We have to study all of the main hadronic channels to accurately estimate the background • We need serious help from theorists to calculate high-order correction to the cross section • Since there are many things to do, a large and experienced team working on that task is necessary PhiPsi 2017, Mainz 26.06.2017 23

Conclusions • Last decade demonstrated the fruitfulness of the flavor “factories” for hadronic cross section measurements via ISR as well as by the direct scan. • At present SuperKEKB/Belle II project is in commissioning. Very high expected luminosity of this experiment provides a possibility of the precise measurements of the hadronic cross section in a wide energy range from production thershold to 11.5 GeV. • We hope that high statistics and improved detector will help to reduce considerably systematic uncertainties. • To provide accurate data, especially for low mass range, we need to care about the proper trigger system and to prepare instruments to control stability of the charge particles and photon reconstruction efficiency during experiment. • There are many things to do for a large and experienced team to cope with this task PhiPsi 2017, Mainz 26.06.2017 24

ISR -Two approaches e + e + higher cross section, but hard photon partial reconstruction, higher background full reconstruction, e + e + low background but lower cross section, hard photon PhiPsi 2017, Mainz 26.06.2017 25