Поликарпов Сергей, 12 апреля 2012, ИТЭФ

1. Поликарпов Сергей, 12 апреля 2012, ИТЭФ Статья принята в Physics Letters B 1 марта 2011

2. Outline • LHCb detector • Decay trees • Data analysis, simulation • Results • ф mode • f0 mode • ratio f0 to ф • Conclusions

3. Детектор LHCb

4. Decay trees

5. Data analysis • 33 1/pb data collected with LHCb detector in 2010 • J /ψ →μ+ μ− : • opposite sign tracks • pT > 500 MeV/c, • identified as muons, • vertex χ2/ndof < 11, • tz = dZ(J/psi)/{Pjp/Mjp} > 0.5 ps • | M(μ+ μ− ) – 3096.9 | < 48 MeV for further analysis 549 , 000 ± 1100 J /ψ signal events in the entire mass range

6. J/psi -> μ+ μ− Crystal Ball function

7. Data analysis(2) • χ2( IP[ pi (or K) ] == 0) > 9 (pi and K tracks do not come from PV), • Perfect pi/K separation with RICH, • Opposite-sign di-pion candidates -> sum pT > 900 MeV • Opposite-sign di-kaon candidates -> • sum pT > 1000 MeV, • |M(K+ K-) – M(φ) | <20 MeV • B0s : two pions(+ and -) (or kaons) form vertex with a χ2< 10, • with the J /ψ they form the B0s vertex: χ2/ndof< 5, • Angle between P(this B0s candidate ) and direction to the PV <0.68◦

8. Simulations to find out efficiency • The efficiencies of having all four decay tracks in the geometric acceptance and satisfying the trigger, track reconstruction and data selection requirements are: • (1.471 ± 0.024)% for J/ψ f0,requiring the π+ π− invariant mass be within ±500 MeV of 980 MeV, • and (1.454 ± 0.021 )%for J /ψ φ ,having the K+ K− invariant mass be within ±20 MeV of the φ mass. • [Monte Carlo events generated using PYTHIA [..], and LHCb detectorsimulation based on GEANT4 [..]. ] • The uncertainties of the efficiencies are statistical only.

9. RESULTS

10. Mass (J /ψ K+ K−) (in φ-> K+ K− mode) 635± 26 events B0s mass =5366.7 ± 0.4 MeV, width = 7.4 MeV Gaus + pol1

11. Mass (J/psi pi+ pi-) Mass(pi+ pi-) = ( 980±90) MeV signal(gaus) 111± 14 signal events within ±30 MeV of the B0s mass 23 ± 9 B→J /ψπ+π− events B0s →J /ψη + B0s → J /ψφ B+→J /ψ K+ (π+)

12. Polarization in f0 mode S(J/ψ ) = 1 S(B0s) = 0 S(f0) = 0 π+ J /ψ rest frame f0 rest frame μ+ θf0 B0s θJ/ψ J/ψ B0s f0 π- μ- θf0 should be distributed uniformly (~const) θJ/ψ should be distributed as [1− (cosθJ/ψ)^2)]

13. Angular distributions of events within ± 30 MeV of the B0s mass and± 90 MeV of the f0 mass after like-sign background subtraction. χ2/ndof = 15.9/9, because of efficiency&background effects [1− a*(cosθJ/ψ)^2)]; a= 0.81± 0.21 (fit result) χ2/ndof = 10.3 / 8 Spin(J /ψ) perpendicular to its momentum and a spin-0 f0 meson.

14. Mass(π+π−) | Mass(J /ψπ+π−) = Mass(B0s) ± 30 MeV 635 +- 26 φ events 265 ± 26 events, including 169(+31−21) f0 (980) events taking into account efficiencises

15. Model-independent result {M(pi pi) = (980±90) MeV , here are 111 ± 14 events.}

16. Conclusions • The first observation of a new CP-odd eigenstate decay mode of the B0s meson into J /ψ f0(980) has been made • Using a fit including two interfering resonances, the • f0(980 ) and f0(1370) ,the ratio to J /ψ φ production is measured as • By selecting events within ±90 MeV of 980 MeV the ratio becomes R’ = 0.162 ± 0.022 ± 0.016. • The events around the f0(980) mass are large enough in • Rate and have small enough backgrounds that they could be used to measure βs without angular analysis.

17. BACKUP SLIDES

18. Crystal Ball

21. Systematic uncertaintaes