International Symposium of Multiparticle Dynamics 2007 09 Aug 2007

International Symposium of Multiparticle Dynamics 200709 Aug 2007 Tania Moulik (University of Kansas)On behalf of CDF & D collaboration

Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

Protons :LINAC Booster Main Injector Tevatron 400 MeV 8 GeV 150 GeV ~1.00 TeVAntiprotons :120 GeV protons (MI) Ni Target antiprotons debuncher+accumulator+recycler Tevatron

6 Km3 Km150 mAccelerator chain


Overview of Detectors


B spectroscopy Motivation QCD simplifies in the limit of one heavy quark mass Heavy Quark effective field theory (HQET). Mass scale for heavy baryons different from quark confinement scale L ~ 400 MeV governing physics of light hadrons. mt, mb, mc >> LQCD >> ms, mu, mdHeavy baryons good way to study non-perturbative QCD (Quark interactions inside hadrons described by non-perturbative QCD)HQET successful in describing Qq systems. Continue to test it for Qqq systems. Features of HQET:Treat heavy quark as static source of color field.In case of baryons, view Light quarks forming a diquark pair and independent of the heavy quark in the limit of infinite heavy quark mass and it looks the same for any flavor or spin orientation of the heavy quarkAlso test Heavy baryon predictions from other theoretical models (approximations to QCD):1/Nc expansion, sum rules, lattice QCD


Experimental timeline of heavy B baryonsFor a long time only known heavy B baryon was Lb.Semileptonic decays observed at LEP between 1992-1998 and also at Tevatron.Hadronic decay modes (Fully reconstructed == Measure mass precisely)(J/Y L) (1991)@UA1 (1997)@CDF Lcp (2006) @ CDF and continued to be studied at Tevatron.Recent discoveries at Tevatron of Sb and Xb, and the excited B states lead to an exciting new era of testing theories describing quark systems with a heavy baryon. Potential to discover other new B baryons, and so on


The quest for b BaryonsLight diquark system : spin 0 (L) (I=0, Jp=0-) / spin 1 (S) (I=1, Jp=1+) state

state (0+) heavy Quark (1/2+), S state (1+) heavy Quark (1/2+) Host of hadron discoveries led Enrico Fermi to exclaim "Had I foreseen that, I would have gone into botany"


Mass predictions and hierarchiesWhy are L and S masses different?

S (uus) L (uds) mass difference believed to be due to difference between u-d and u-s hyperfine interactions :

And other predictions :Hyperfine splittingsZeldovich, Sakharov, Sov. J. Nucl. Phys. 4(1967) 283Predicted mass hierarchy: M(b)< M(b) < M(b) Karliner, Lipkin, hep-ph/0307243, Phys. Lett. B 575, 249(2003)


Observation of SbIn Sb light quarks in symmetric state

Together with heavy quark leads to doublet of baryons

Ground state S decays strongly to L-type baryons (antisymmetric configuration of quarks) emitting pions. Look for Sb in decay mode Lb p. Number of theoretical predictions:

180 210 MeV10-40 MeV (Mass splitting)5-7 MeV0.400.07 MeV (Isospin splitting)


Sb Lb p, Lb Lc p, Lc p K pStart with constructing Lb Then, Search for narrow resonances in the mass difference distribution

Backgrounds: tracks from Lb fragmentation (e.g. hadronization of the b quark) and underlying event.Physics background,B0 D-p+; D- p-K+p-Also B0s from B** decays.Optimize cuts with Sb signal region blinded.

Lb ct(PDG) = 422 mm, Cut requirement:ct (Lb) > 250 mm5.565 < m(Lb) < 5.670 GeV


Sb ResultsFit to breit-wigner convoluted with double gaussian. Width of breit-wigner :

No isospin splitting sensitivity

Measure average


Observation of Xb (dsb)Vertex Prob c2 > 1 %pT (m) > 1.5 GeV2.80 GeV < M (mm) < 3.35 GeVpT (J/Y) > 5 GeVVertex Prob c2 > 1 %Track with higher mom. Assumed pion1.05 GeV < M (pp) < 1.125 GeVAt most 2 hits in tracker before pp vertex. Imp. Param sig. > 3(both tracks)At least > 4 (for one track)Imp. Param sig. > 3(pion track)Decay length (L) > 4 * uncertaintyDecay length (X) > 4 * uncertainty


Special techniques..For particles like the b-, usual impact parameter cut requirement for track reconstruction could result in missing the and proton tracks from the and - decays.At D entire J/Y dataset was processed with special extended tracking: Impact parameter cut from 2.5 cm 10.0 cm Maximum acceptance angle Df 0.08 rad 0.2 radAt CDF X candidate tracks are refitted, with Si hit requirements.p--


Xb Results Likelihood Fit Results : M (D) = 5774 11 (stat.) 15 (syst.) MeV -- [1]M (CDF)= 5792.9 2.4 (stat.) 1.7 (syst.) GeV ) [2] (Theory : 5.793 - 5.814)15.2 4.417.5 4.3[1] PRL 99, 1052001 (2007)[2] arXiv:0707.0589


Observation B1 and B2*Among B mesons, Only ground 0- states B+,B0,Bs,Bc and excited 1- state B* considered established.Quark models predict 2 broad and 2 narrow P-states:

Broad states difficult to distinguish Width ~ 100 MeV (Decay through an S wave). Narrow states easier to identify Width ~ 10 MeV (Decay through D wave)

M..Di Pierro and E. Eichten, Phys. Rev. D 64 (2001)


Observation B1 and B2*Look for mesons in decay modesReconstruct Look for p track from primary vertex. Combine with B+Plot Breit-wigner convoluted with gaussian. Resolution in DM determined fromsimulationPDG, J. Phys. G 33 1 (2006)


Observation B1 and B2*Unable to resolve the B2* decaying through B* and emission of g and through B.Masses agree to within 1 s

D0 CDFM(B1) (MeV)5720.62.4 1.4M(B2*) (MeV)5746.82.4 1.7


Observation of Bs*Analysis similar to previous modeLook for the decay B*s2B+K-Where is B*s2B* K ? should be here

Claim : Suppressed due to L=2 orbital angular momentum and small mass differenceD0 does not observe the Bs1 peak. Would be interesting to look at more data.


Bs* Interpretation and TheoryTheory predicts equal branching ratios of Bs2* B*+K- and B+K-. Experimentally should be observed as resonance displaced to lower DM by photon energy 45.78+-0.35 MeV.Rate supressed by a factor (No signal expected with current statistics)

What about Bs1 B*K+?In (bd) system, M(B2*) M(B1) = 26.2+-3.1+-0.9, ..Applying to Bs systemExpect Bs1 = 5813 MeV i.e. < M(B*)+M(K-) (5819 MeV)In this case, no Bs1 signal expected.C.M. Momentum of K in B*K decayC.M. momentum of K in B K decay


Results Bs*


B Quest began and continues @ FermilabCelebrating 30 years of the b quark discovery @ FermilabA fitting anniversary celebration: Discovery of new B baryonsand the search goes on!1977


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International Symposium of Multiparticle Dynamics 2007 09 Aug 2007