1. Is there any light sbottom? Introduction Existing limits Direct search conclusion M. Antonelli STF 12/7/00

2. Introduction CDF anomaly in jet data interpreted as sbottom production: unofficial discussion with CDF friends not official under review by the collaboration b -> c l v ~ ~ Sbottom mass around 3.6 GeV /c 2 ! ! ! About 1 ps of lifetime (  0.4 ps) with a dominant vector matrix element What’s about the existing limits? Almost massless sneutrino ! ! ! l= ,e

3. Z width constraints  z (inv) =498.8  1.5 ~ Most severe limits derives from invisible Z width measurements This limit is overcame only if sneutrino mixing is assumed massless v L excluded (not a news)  z (inv extra SM) < 1.7 MeV v 1 = cos  v L +sin  v R ~ ~ ~ v 2 mass has to be above the Z width limit ~ Z width constrain cos  <1/7 for m v =0 (G.Ganis)  z (inv)theo =501.6

4. More about sneutrino mixing Large mass splitting is needed to avoid LEP1 limits: possible only with SUSY see-saw ( Yuval Grossman, Howard E. Haber Phys.Rev.Lett. 78 (1997) 3438-3441 ) LEP1 constraints can be used to check consistency with the ~1ps lifetime (width calculation done to be included in MSMLIB)  m v ~2(A v -  cot  -B N )m v /m v ~ ~~ m v =(m v1 +m v2 )/2 ~~~ B N :SUSY breaking term associated to right-handed neutrino superfield

5. Z width constraints  z =2494.4  2.4 Z width measurement constrain also sbottom production limit for the sbottom mixing angle for a mass of 3.6 GeV  z (extra SM) < 6.2 MeV (G.Ganis)  z theo=2493.8

6. Cross section measurement constraints Low energy data: SM SM + sbottom (Z dec.)

7. Cross section measurement constraints LEP2 hadronic cross section:  sbottom~1%

8. Limits for bound states bb bound states production in e+e-: Low energy limits for bb bound state production in e+e-:  ee < 60 MeV (Mark1)  ee(2p)~ 15 MeV ~~ - 16 pb/MeV

9. What about b-factory bb cross section in the b-factory energy range: About 3000 sbottom events/day (BaBar) ~~ - ~~ Pep-II is delivering ~100 pb -1 /day Z-decoupling

10. Experimental signature at LEP2 e+e- -> bb (b-> c l v): two back to back leptons + 2 jets with content no ISR Z return (Z width limits) Lepton id + b-tag Main background: semileptonic bb - ~~ - ~ ~

11. Selection Preselection: nch>7 etot/elep>0.55 s’/s > 0.5 Thrust >0.975 cos(  Thrust ) > 0.95 log(P uds )<-0.2

12. Selection

13. Cuts and Performances Cuts optimized with N95 for m b =3.6GeV and 1 ps lifetime 2 back to back opposite charge leptons: Electron ID: RT>-3, 3>RL>-3 Muon ID: QMUIDO flag [=11(HCAL).OR.  13(HCAL+  ch)] el1/elep>0.02 el2/elep>0.01 |  -180 o |<8 o at 200 GeV (scaled with the boost) log(P uds ) 0.7 Elep L (pb -1 ) bkg eff  95  sign(min) 189-202 411 23.9 27% 108 fb ~200 fb Bkg composition: 23.8 qq 0.1 4-fermion (78% bb 18 % cc 4% uds)

14. Results Bkg ex. 10.7 1.7 4.4 4.6 2.5 23.9 Data 19 1 6 8 5 39 Systematic effects: b-tag, lepton id (good agreement at pre. level) MC simulation of heavy flavor at high energy KORAL08 at Z vs Hvfl06 ~ 3  deviation Analysis of 411 pb -1 at 189-202 GeV Elep 189 192 196 200 202 tot

15. Results + Bkg ex. 1 1 3.6 4 9.6 33.6 Data 1 4 9 3 17 56 ~ 3.8  deviation Prob(N  Nobs,Nbkg) = 2.5 x 10 -4 If 10% systematics on Bkg is added: Prob(N  Nobs,Nbkg) = 0.2% Analysis of 10+10+57+94 pb -1 at 161- 172-183- >202 GeV Elep 161 172 183 >202 tot ALL data (169-208)

16. Checks at Z Same selection as H.E.(KORAL08)  Thrust log(P uds ) El1/elep El2/elep MC stat ~2xdata Data=374 MC = 358  =(4  6)%

17. Checks at Z Hvfl06 MC statistic ~4xdata  Thrust log(P uds ) El1/elep El2/elep

18. Sbottom Matrix element CDF interpretation include a vector matrix element: c and lepton in the same direction -> larger missing energy with respect to hvfl semileptonic decays Check etot/(elep*(s’/s) 1/2 )

19. Sbottom Matrix element Check etot/(elep*(s’/s) 1/2 ) at the Z KORAL08 Hvfl06

20. Conclusions  CDF interpretation of unofficial jet anomaly excluded in the standard MSSM scenario (v L ) -> invisible  Z î Existing measurements are not able to exclude light sbottom  Dedicated searches 3.7  deviation (3.0 including 10% systematics on SM bkg) î Statistical fluctuation? Systematic effect? What about b-factory? î sneutrino mixing can have an impact on SUSY searches