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The start of the Belle II experiment at the SuperKEKB e + e - factory

The start of the Belle II experiment at the SuperKEKB e + e - factory. Bo s tjan Golob University of Ljubljana/ Jozef Stefan Institute also with. Introduction B-Factories Belle II Luminosity Performance Measurements. “Jo z ef Stefan” Institute. University of Ljubljana.

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The start of the Belle II experiment at the SuperKEKB e + e - factory

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  1. The start of the Belle II experiment at the SuperKEKBe+e-factory Bostjan Golob University of Ljubljana/ Jozef Stefan Institute alsowith Introduction B-Factories Belle II Luminosity Performance Measurements “Jozef Stefan” Institute University of Ljubljana 3rd Jagiellonian Symposium on Fundamental and Applied Subatomic Physics Krakow 23 - 28 June 2019

  2. Introduction electromagnetic weak strong gravitational Setting the scene The Standard Model (SM) of basic interactions in Nature - - one of the experimentally best verified physics theories... ...at the current level of experimental precision andenergies reached Several severe shortcomings, for example degree of CP asymmetry between particles and anti-particles; responsible for matter dominated Universe, tested in subatomic world; 10 orders of magnitude too low to explain the matter / anti-matter asymmetry of Universe search for physics phenomena beyond SM, new particles, and new interactions often addressed as New Physics (NP)

  3. B Factories B e- e+ Dz ~cbgtB ~ 200mm B TEST of Kobayashi-Maskawa Mechanism B-Factories, e+e-: BaBar (SLAC)/Belle (KEK)1999 – 2010 B0 J/yKS Lmax=2.1 1034 cm-2s-1 Belle: N(BB) 770 106 sin2f1 from B J/y KS B0 J/yKS √s=10.58 GeV 2008: M. Kobayashi, T. Maskawa U(4S) n.b.: only to Dmd 32 measurements contribute! -6 -4 -2 0 2 4 6 Dt [ps] U(4S) I. Adachi et al. (Belle Coll.), Phys. Rev. Lett. 108, 171802 (2012) p(e-)=7GeV p(e+)=4GeV bg≠0

  4. Belle II Super B-Factory: SuperKEKB & Belle II (KEK) 2018  Access B decays with erecBr >~10-9 (e.g. erec Br(B h‘KS) ~ 1 10-6 erec Br(B Xdg) ~ 1 10-7 erec Br(B Xutn) ~ 4 10-8 erec Br(B K(*)nn) ~ 7 10-9 ) L=2 1034 cm-2s-1  L=8 1035cm-2s-1 explore possible deviatons from SM prediction appearing in some rare decays N(BB)  50  NBelle(BB)

  5. Belle II DetectorBelle II KL and muon detector: Resistive Plate Counter (barrel outer layers) Scintillator + WLSF + MPPC (end-caps , inner 2 barrel layers) EM Calorimeter: CsI(Tl), waveform sampling (barrel) Pure CsI + waveform sampling (end-caps) Particle Identification Time-of-Propagation counter (barrel) Prox. focusing Aerogel RICH (fwd) electrons (7GeV) Beryllium beam pipe 2cm diameter Vertex Detector 2 layers DEPFET + 4 layers DSSD positrons (4GeV) Central Drift Chamber He(50%):C2H6(50%), small cells, long lever arm, fast electronics

  6. Luminosity Luminosity plans end 07/19 start 03/19 start 10/19 end ? 07/19 Phase 1 Phase 2 Phase 3 → Phase 1: w/o QCS w/o Belle 2 Phase 2: w/ QCS w/ Belle 2 (no VXD) Phase 3: full Belle 2 dailyLdt [pb-1] QCS, Belle 2 VXD LHCb LS2 ~ 50ab-1 HL LHC LHCb LS3 Ldt [fb-1] Plan: reach KEKB luminosity in June 2020 > 100 fb-1 by end of 2020 spring run current issues: fire (4/2019, not related to SuperKEKB,~2 weeks recovery) injection bkg (reduced with machine and collimators tuning) storage backgrounds (mainly beam-gas, vacuum scrubbing, additional pumps)

  7. Performance Physics performance A. Sangal et all. (Belle II Coll.), BELLE2-NOTE-PL-2018-035 S. Longo, J.M. Roney et all. (Belle II Coll.), BELLE2-NOTE-PL-2018-027 fK+K- p0→ gg no requirement on g at least one g passing loose PSD at least one g passing tight PSD hadron veto in ECL using Pulse Shape Discrimination combined pid (TOP, CDC, ARICH)

  8. Performance Full Event Interpretation only a single BB pair produced @ U(4S) FEI performed using MVA etag~ 0.2%-0.3% @ P~50%-60% recontruction of final states with undetected particles detected hadrons Btag e+ e- n Bsig K- D(*) p + l B+ B0 W. Sutcliffe, F. Bernlochner, B2NOTE-2018-031-1

  9. Measurements Lepton Flavor Universality B →D(*)ln t -, l= e-, m- b c D*+l - Nsig=376 ±36 W - n u D(*)0 B- S.Fajfer et al., Phys.Rev.D85(2012) 094025 R(D*)SM = 0.252 ±0.003 R(D)SM= 0.300 ±0.008 H. Na et al., Phys.Rev.D 92, 054410 (2015) A. Abdesselam et al. (BelleColl.), arXiv:1904.08794 R(D)= 0.307±0.037 ±0.016 R(D*) = 0.283±0.018 ±0.014 Belle II (50 ab-1) WA SM E. Kou, P. Urquijo eds., The Belle II PhysicsBook to be published in Prog. Theor. Exp. Phys.

  10. Measurements CPV in b→sqq some uncertainties cancel in DS vtxreconstr. improved with better tracking; erec Br(B h‘KS) ~ 1 10-6 41 new phases in MSSM; b→sqq B → J/yKs s(sin2f1eff) DS=sin2f1eff -sin2f1 E. Kou, P. Urquijo eds., TheBelle II PhysicsBook to be published in Prog. Theor. Exp. Phys.  s~12 mm w(p+p-p0)Ks Belle: s~30 mm f(K+K-)Ks h‘(ggpp)Ks   s(sin2f1) fromB → J/yKs  currentth. uncertainty Ldt[ab-1] N. Braun et all. (Belle II Coll.), BELLE2-NOTE-PH-2018-040 M. Beneke, PLB620,143 (2005)

  11. Summary • Belle & BaBar: confirmed CKM mechanism • SuperKEKB: start of data taking in 2018 • luminosity gradually increasing • Belle II: ~900 members (~45% from Europe), 26 countries • detector operating as expected • search for NP • Lepton Flavor Violation • Lepton Flavor Universality • new sources of CPV • light dark matter • : Physics (far) beyond current theoretical understanding (SM) Severe constraints on possible beyond SM theories

  12. Suplementary Material

  13. Standard Model Setting the scene • The Standard Model (SM) of basic interactions in Nature - • - one of the experimentally best verified physics theories... • ...at the current level of experimental precision andenergies reached • Several severe shortcomings • for example • (too) large number of free (to be measured, unexplained) parameters • degree of CP asymmetry between particles and anti-particles, • 10 orders of magnitude too low to explain the matter / anti-matter • asymmetry of Universe • Dark Matter (25% of Universe) completely unknown search for physics phenomena beyond SM, new particles, and new interactions often addressed as New Physics (NP)

  14. CKM TEST of Cabibbo-Kobayashi-Maskawa VCKM must be unitary  unitary triangle various B meson processes  sides & angles of unitary triangle c W - qd qu u Vquqd D(*)0 B- b l -, qd W - n, qu Vquqd Vcb n.b.: only to Dmd 32 measurements contribute!

  15. CKM • TEST of Cabibbo-Kobayashi-Maskawa • joint analysis of Belle & BaBar data • 1.24 109BB pairs • B0  D0(KSp+p -) h0 • h0=p0,h,w • enables determination of cos2b • (not only sin2b as in B0  J/yKS ) Btag=B0 Btag=B0 mp+p-~ r(770) mKsp~ K*(892) cos2b =0.91± 0.22 ± 0.09 ± 0.07 (model) B0 J/yKS (b  ccs) Belle: sS~0.03 Belle II: sS ~ 0.004

  16. Performance Physics performance V. Bhardwaj et al., BELLE2-NOTE-PL-2018-012 A. Sangal et al., BELLE2-NOTE-PL-2018-031 D*+→ D0(K-K+)p+ D*+→ D0(K-p+)p+ V. Bhardwaj et al., BELLE2-NOTE-PL-2018-022 CombinedPID (TOP, ARICH, CDC) D*0→ D0(K-p+)p0

  17. Performance Physics performance testing analysis tools from low to high level vertexing (SVD, PXD) unapproved

  18. Performance Physics performance testing analysis tools from low to high level V. Bhardwaj et al., BELLE2-NOTE-PL-2018-012 D*+→ D0(K-p+)p+ Combined PID (TOP, ARICH, CDC) A. Gaz et al., BELLE2-NOTE-PH-2019-004 B →D*ln D* partial reconstruction Nsig= 282 ± 25 unapproved Nsig= 51 ± 15 l B n B D* p + Leptons (ECL, KLM) l opposite sign leptons (no mixing) same sign leptons (mixing)

  19. Accelerator Phase 2:acceleratoranddetectorcomissioning, physicscollissions validationof Nano beamscheme March – July 2018 KEKB: sx~100mm,sy~2mm Belle: s ~ 1 cm SuperKEKB: z0ofsingletracks fromprimaryvtx sx~10mm,sy~60nm N. Braun et al., BELLE2-NOTE-PL-2018-008

  20. LFU TESTS of LFU in B decays; HL,T : form factorsparametrizing unknown QCD effects cancelationof some theoreticalandsyst. uncertainties b c W - l= e-, m-,t - u D(*)0 B- n R(D*)SM = 0.252 ±0.003 S.Fajfer et al., Phys.Rev.D85(2012) 094025 R(D)SM= 0.300 ±0.008 H. Na et al., Phys.Rev.D 92, 054410 (2015)

  21. LFU TESTS of LFU Br(B →Dln) ~ 2% problem? Btagreconstruction e+e-→ U(4S) → BtagBsig hfromBsig→hX; no extraenergy in calorim.; signalEECL~0; Btagreconstruction NeuroBayes, neuralnetwork erec~0,5% D(*)0 B- neutrinos! (B →Dt(→ enent)nt) l=e-,m-,t - e+ n n BtagBsig e-

  22. LFU exampleofmeasurement detected hadrons Btag Belle, PRD92, 072014(2015), 700 fb-1 e+ e- n Bsig K- D(*) p + l singlen Mmiss2=Mn2 0 Nsig=503 D* t n Nsig=320 D t n Nsig~ 3800 D* l n Nsig~ 3150 D ln systematicchecks: bkg‘sfromB  D** ( D* p )l n ; selectD* p l n decays checksofdistributions D**l n R(D)= 0.375±0.064±0.026 R(D*) = 0.293±0.038±0.015

  23. LFU A. Abdesselam et al. (BelleColl.), arXiv:1904.08794 Belle Semileptonictagging D*+l → D*0l → full NN range signal NN range NN: signal/normalization EECL: signal+normaliz. / bkg. fit: D(*)tn, D(*) l n, feeddownfromD(*)l (t)n, D**l (t)n, otherbkg., shapefrom MC

  24. LFU Lepton Flavor Universality B →D(*)ln t -, l= e-, m- b c D*+l - Nsig=376 ±36 W - n u D(*)0 B- S.Fajfer et al., Phys.Rev.D85(2012) 094025 R(D*)SM = 0.252 ±0.003 R(D)SM= 0.300 ±0.008 H. Na et al., Phys.Rev.D 92, 054410 (2015) A. Abdesselam et al. (BelleColl.), arXiv:1904.08794 R(D)= 0.307±0.037 ±0.016 R(D*) = 0.283±0.018 ±0.014 6.0% s(RD)/RD[%] 3.6% s(RD*)/RD*[%] 0.14 s(Pt) [x10] Ldt [ab-1] E. Kou, P. Urquijo eds., The Belle II PhysicsBook to be published in Prog. Theor. Exp. Phys.

  25. CPV in b→sqq CPV in b→sqq some uncertainties cancel in DS (vtxreconstr., flavor tag, likelihood fit) ; better KS eff. with vtx hits - larger vtx radius, 30%); vtxreconstr. improved with better tracking; 41 new phases in MSSM; b→sqq B → J/yKs s(sin2f1eff) DS=sin2f1eff -sin2f1 E. Kou, P. Urquijo eds., TheBelle II PhysicsBook to be published in Prog. Theor. Exp. Phys.  vtxresol. B→f(K+K-)Ks 2.1 ps iptube, Ks → 0.75 ps w(p+p-p0)Ks f(K+K-)Ks h‘(ggpp)Ks (B→h‘(ggpp)Ks B→w(p+p-p0)Ks → 1.25 ps)   s(sin2f1) fromB → J/yKs  currentth. uncertainty Ldt[ab-1] M. Beneke, PLB620,143 (2005)

  26. t leptons t Lepton Flavor Violation A.Lusiani, EPPSU2019, may 2019 CLEO Belle/BaBar Belle II/HL-LHC t  mg at e+e- t+t- backgrounds from e+e- m+m-g andt  mnn + noise g BrUL1/L t  3m at e+e- t+t- almost background free BrUL1/L

  27. B → K(*)l+ l - l - B → K(*)l+ l - R(K(*))= B(B K(*)m+m-) / B(B K(*)e+e-) ql qK* B LHCbColl., LHCb-Paper-2019-009 p K* K l + K+e+e- RK=1 K+m+m- q2=m2(l + l -)

  28. B → K*m+ m- angular distrib. B → K*m+ m- P5‘: one of ang. distr. variables w/ reduced th. uncertainty LHCbColl., JHEP09 179 (2015) several b  smm processes Bs→ fm+ m- B0→ K0m+ m- LHCbColl.,JHEP 06 133 (2014) NP LHCbColl., JHEP02 104 (2016) Belle Coll., PRL118 111801 (2017) Atlas Coll., JHEP10 047 (2018) CMS Coll., PLB781 517 (2018) new data from LHCb / Belle II being recorded as we speak

  29. B K(*)nn BK(*)nn FEI, had. Tag; 4p*miss = 4p*(U(4S)) -- 4p*(Btag) – 4p*(K*) E*miss+ p*missisolates signal; influence of beam bkg. on FEI not crucial; erec (K*  Kp) ~ 5 10-4 sig, arb. norm. bkg signal MC selection BB MC s(Br(BK*0nn)) Br(B K*0nn) EECL EECL BKGx1 BKGx0 + 18% (combined semil. + had. tag) s(FL(K*0)) similar for K*+and K+ Ldt[ab-1]

  30. B K(*)nnB(s)nn BK(*)nn Cl,rNP allowed 68% C.R. from Br(B K*nn), Br(B Knn) & FL(B K*nn) @ 50 ab-1 (Cl,rNP Real, n flavor independent) s(Cl,rNP) ~ 0.1 – 0.2 B(s)nn Br( Bnn) < 1.5 10-6 @ 50 ab-1 Br( Bsnn) < 1.1 10-5@ 5 ab-1 (U(5S)) Br(BK*nn) FL(BK*nn) Belle, BaBar excluded Br(BKnn)

  31. DM Dark sector, e+e- m+m- Z‘, Z‘ invis. identified by m+m- recoil mass; expected UL on g‘ (Z ‘ coupling to m and t) expected UL with Phase II data value for (g-2)m discrepancy explanation M. Bertemes et al. (Belle II Coll.), BELLE2-NOTE-PH-2019-002

  32. DM Dark sector, e+e- ga, a gg for low ma two merged g‘s, same as e+e- gg, trigger not to veto or prescale M. de Nuccio, T. Ferber et al. (Belle II Coll.), BELLE2-NOTE-PH-2019-005

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