Λb and heavy states at Tevatron by Eduard De La Cruz Burelo University of Michigan On behalf of CDF and D0 collaborations Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Outline: Tevatron & Detectors Λb quick overview Physics with the Λb Λb at Tevatron Reconstruction Semileptonic decays channels Full reconstructed decays channels Mass measurement Lifetime measurement Branching Fractions B** B decays to narrow D** Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Overview on the Λb Lightest b baryon (udb) First observed by AU1 collaboration in 1991 in the decay channel Λb→J/ψΛ. First lifetime measurement from LEP experiments using semileptonic decays in 1992. Currently produced in high statistics only at Tevatron, (non produced in B factories) Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Rich physics program in the Λb Testing HQE theory in b baryons (lifetime) Spin role in heavy hyperons (polarization) CP violation T violation ( ) New physics ( ) Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Experimental status PDG’04 Lb Other b-baryons Mass (σM~0.16%) Lifetime (σct~6.5%) Decay channels: Λ+c l- ν X (BR, σBR~23%) J/ψΛ (BR, σBR~60%) Λ+cπ- (seen) Λ+ca1(1260)- (seen) pK- , pπ- , Λγ upper limits Some indirect lifetime estimations Some “seen” decay channels Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

A lot of theoretical work Example … LO NLO C. Tarantino, Monday 20 This was just less of a couple of years ago. This was just less of a couple of years ago. A lot of theoretical work Just last month !!! HFAG hep-ex/0505100 (*) Includes D0 and CDF Run II measurements (*) Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

First step: “Reconstruction” Quite a challenge For both detectors: Only charge particles reconstructed A lot of things going on in the silicon detector Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Reconstruction of the Λb Tevatron is like a B factory, but a dirty one Only ~5% reconstructable Zoo of b hadrons: B0, B+, Bs, Bc, b,  b, B** But: O(103) higher Difficult to find other b In b events , only fb~ 10% (b→X) Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Λb in full reconstructed channels Both experiments have clear signal of Invariant Mass, (GeV/c2) Invariant Mass, (GeV/c2) Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Λb in full reconstructed channels Invariant Mass, (GeV/c2) PDG’04 : Seen! Now: clear evidence Λb→Λ+cπ - ~ 11σ Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Λb in semileptonic decays Toward the direct measurement of τ(Λb)/τ(B0d), similar to τ(B+)/τ(B0d) [PRL 94, 182001 (2005) ] Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

After reconstruction … Mass measurement Lifetime Branching fractions Etcetera … Lb Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Most precise Lb mass measurement in the world !!! Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Simultaneous Mass & lifetime likelihood fit Lifetime measurement Signal selection λ + mass distribution (signal + bkg) Fit procedure Models for λ + mass distribution Background (λ) Signal (λ) Background (λ) Models: Simultaneous Mass & lifetime likelihood fit Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

First measurement in a full reconstructed decay channel !!! Λb lifetime[1] DØ DØ First measurement in a full reconstructed decay channel !!! [1] V.M Abazov et al, PRL 94, 100201 (2005) Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Branching fractions: Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Branching Fraction: Lb → Lc p From PDG: 1.84±0.493 From MC: 1.65±0.03 From the fit: NΛb=214±19(stat) NB0=790±32(stat) Assuming: (PDG ’04) Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Branching Fraction: Bsemi/Bhad First measurement of this ratio !!! Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Search for Lb→hh decays Prediction[2]: Br (Lb→ pK)=(1.4-1.9)×10-6 Br (Lb→ pp)=(0.8-1.2)×10-6 compare to Br(B0→Kp)= 18×10-6 Large CP asymmetries O(10%) expected in b-baryons Previous best limit from ALEPH BR(b pK) < 50x10-6 @ 90% BR(b p) < 50x10-6 @ 90% [2] Mohanta, Phys. Rev. D63:074001,2001 Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

B1 & B*2 observed by first time as separate states!!! B** resonances B meson spectroscopy only well established for ground states B+,B0,Bs. Few models with precise predictions: mass/widths/BR B1 & B*2 observed by first time as separate states!!! Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

BD**mn BsDs**mn Semileptonic decays to excited states Ds**D*KS Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch

Summary A lot of new results from Tevatron on the Lb baryon Best mass measurement First lifetime in full reconstructed channel Branching fractions by first time measured More in preparation: Direct lifetime ratio measurement τ(Λb)/τ(B0) Others b baryons and studies… CDF and D0 are looking forward to contribute to a best knowledge of the b baryons. Beauty 2005, Assisi (Perugia) Italy Eduard.Burelo@cern.ch