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

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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

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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

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μ / KL detection

14/15 lyr. RPC+Fe

Central Drift Chamber

small cell +He/C2H6

CsI(Tl)

16X0

Aerogel Cherenkov cnt.

n=1.015~1.030

Si vtx. det.

3/4 lyr. DSSD

TOF counter SC solenoid

1.5T

8 GeV e− 3.5 GeV e+

F/B asymmetric detector High vertex resolution, magnetic spectrometry, excellent calorimetry and sophisticated particle ID ability E− = 8 GeV, E+ = 3.5 GeV, √s=10.58 GeV, βγ=0.42 Peak lumi record at KEKB: L=2.1 x 1034/cm2/sec with crab cavities The primary goal of the Belle and BaBar experiments was to discover the CP violation in B mesons and to measure the parameters of CPV. This was achieved by both experiments in 2001

1 2010 1999

1

−

=

∫

ab Ldt

Belle Detector

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Other important results

  • Observation of direct CP violation in B decays
  • Measurements of the CPV parameters in different modes (φK0, η′K0,

KSKSKS, …)

  • Measurements of rare decay modes (e.g., Bτν, Dτν)
  • Observation of new charmonium-like and bottomonium-like hadronic

states

  • bs transitions: probe for new sources of CPV and constraints from the

bsγ branching fraction

  • Forward-backward asymmetry (AFB) in bsl+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−(γISR)

processes So wide research area became possible because of clean event environment and well defined initial state in the e+e− experiments as well as high luminosity and general-purpose detectors

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R(s) measurements at Belle

Direct e+e− scan ISR: with γISR detection, full reconstruction ISR: mostly without γISR detection

PDG

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Rb: Data and Fit

rad. ) 0.4 (-1.0 10860) (

  • 11020)

( MeV ) (61 MeV/c ) 5 . 10987 ( M MeV ) (53.7 MeV/c ) 3.2 (10891.1 M

1.4 0.1

  • 2

20

  • 9

19 11020 2 9 1 . 2 6.4 5 2 11020 1.3 5.4

  • 7.1

5.6

  • 10860

2 0.6 1.7

  • 10860

+ + + − + − + + + +

± = = Γ = = Γ ± = φ φ

.

  • PRD 93, 011101(R) (2016)
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Contribution of exclusive cross sections to the total cross section

DD DD* D*D* DDπ DD*π DsDs +DsDs*+Ds*Ds* ΛcΛc Results on XYZ states will be presented by R.Mizuk

σ(e+e−→D(*)D*)

  • Phys. Rev.Lett. 98, 092001 (2007)

e+e−→ D0D–π+ Phys.Rev.Lett.100,062001(2008) e+e− → Ds(*)Ds(*) Phys.Rev.D 83, 011101 (2011) e+e–→Λc

+Λc –

Phys.Rev.Lett. 101,172001(2008)

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Contribution of exclusive cross sections to the total cross section

BES: Rtot – Ruds; Belle : ∑Rexcl

Results on XYZ states will be presented by R.Mizuk

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e+e− → φ π+π− and e+e− → f0(980)π+π−

PRD 80, 031101 (2009)

673 fb-1

Cross section Syst. Errors - 8.6% and 6.9% M (φ(1680)) = (1689±7±10) MeV/c2, Γ(φ(1680)) = (211 ± 14 ± 19) MeV/c2 M (Y(2175)) = (1689±7±10) MeV/c2, Γ (Y(2175)) = (211 ± 14 ± 19) MeV/c2

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Published ISR results at Belle

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Fred Jegerlehner, arXiv:1705.00263v1 [hep-ph] 30 Apr 2017

Why do we need low energy hadronic cross section?

Past and future of muon (g – 2) experiments

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Fred Jegerlehner, arXiv:1705.00263v1 [hep-ph] 30 Apr 2017

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Contributions of various final states to hadronic vacuum polarization (HVP) term of am

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ISR measurements at BABAR

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Data from BES III (Tau 2016)

Yaqian WANG, Tau-2016

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Belle: low mass ISR study

Belle systematic error goal is 5% But difficult to achieve. 526.6 fb-1 (preliminary, suspended?)

Main problems: Improper trigger Lack of manpower: 2-3 people only vs ~20 at BaBar

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Nano-Beam SuperKEKB

KEKB

σx~100μm,σy~2μm σx~10μm,σy~60nm

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17 KL and muon detector: Resistive Plate Counter (barrel outer layers) Scintillator + WLSF + MPPC (end-caps , inner 2 barrel layers) Particle Identification Time-of-Propagation counter (barrel)

  • Prox. focusing Aerogel

RICH (forward) EM Calorimeter: CsI(Tl), waveform sampling electronics (barrel) Pure CsI + waveform sampling (end-caps) later Vertex Detector 2 layers Si Pixels (DEPFET) + 4 layers Si double sided strip DSSD Central Drift Chamber Smaller cell size, long lever arm

electrons (7GeV) positrons (4GeV)

Belle II Detector

+ New software, improved tracking, ... + Optimization for low multiplicity trigger + Improved simulation, generators and GRID All details are in the Changzheng YUAN talk

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18 Calendar Year

Integrated luminosity ab-1 peak luminosity, cm-2s-1

Expected Luminosity

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ISR at Belle II vs. BESIII

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), γX(3872), π+ π-X(3872), π+ π-hc, π+π-hc(2P), ωXcJ, φ XcJ, ηJ/Ψ, η’J/Ψ, ηΨ(2S), η hc]; and charm meson pair+light hadrons [DD, DD*, DD*π, . . . Chengping Shen, Photon 2017

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⎭ ⎬ ⎫ ⎩ ⎨ ⎧ − − + = ) 1 (ln ) ( πs 2

2 2 4 e

m s m s s m s αm Ldm dl

KEKB VEPP- 2000 BEPC-II Luminosity, см-2 s-1 8⋅1035 1032 1 fb-1 1 fb-1 1033 Integrated lum. (per 107 s) 8000 fb-1 10 fb-1 Integrated in the range [1-2] GeV 8 fb-1 (~0.8 @ cosθ<0.7) Integrated in the range [2-3] GeV 20 fb-1 (~2 @ cosθ<0.7) 10 fb-1

Potential of ISR for low energy range

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Improvements at Belle II relevant to low mass ISR Trigger

Using the Bhabha topology, sum back to back TCs Energy. Bhabha in CM frame

γ

Hadr. Belle Belle II

  • 1. Improved Bhabha veto logic for Belle II
  • 2. Several independent trigger modes are invented to monitor

and check the trigger efficiencies

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22 longer lever arm Improved momentum resolution and dE/dx

Belle Belle II inner most sense wire r=88mm r=168mm

  • uter most sense wire

r=863mm r=1111.4mm Number of layers 50 56 Total sense wires 8400 14336 Gas He:C2H6 He:C2H6 sense wire W(Φ30μm) W(Φ30μm) field wire Al(Φ120μm) Al(Φ120μm)

Improvements at Belle II relevant to low-mass ISR Central Drift Chamber

normal cell

10~20 mm 18 mm 10 mm 6~8 mm

small cell

Belle Belle II Better momentum resolution – better invariant mass resolution

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Systematic uncertainties of BaBar measurements (PRD 86, 032013 (2012))

In general higher statistics provides more possibilities to study systematics Can we improve systematics at Belle II? To try to do that we need to:

  • Continuously and carefully monitor the trigger efficiency, track and

photon reconstruction efficiency and PID (mostly m/p) efficiency

  • 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

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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

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ISR -Two approaches

e+ e+

hard photon

e+ e+

hard photon

higher cross section, but partial reconstruction, higher background full reconstruction, low background but lower cross section,

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e- 7 GeV 2.6 A e+ 4 GeV 3.6 A

x 40 Increase in Luminosity SuperKEKB

Colliding bunches Damping ring Low emittance gun Positron source New beam pipe & bellows Belle II New IR

TiN‐coated beam pipe with antechambers Redesign the lattices of both rings to reduce the emittance Add / modify RF systems for higher beam current New positron target / capture section New superconducting /permanent final focusing quads near the IP Inject low emittance electrons Inject low emittance positrons Replace short dipoles with longer ones (LER)

L = γ± 2er

e

1+ σ y

*

σ x

*

⎛ ⎝ ⎜ ⎞ ⎠ ⎟ I±ξ±y βy

*

RL Ry ⎛ ⎝ ⎜ ⎞ ⎠ ⎟