1 ISMD 2005I. Ripp-Baudot Heavy flavour production results from DØ Run II Isabelle Ripp-Baudot IReS Strasbourg / IN2P3 for the DØ collaboration International Symposium on Multiparticles Dynamics Kroměřίž, August 9-15, 2005

2 ISMD 2005I. Ripp-Baudot Outline Tevatron Run II and the DØ detector Spectroscopy : - X(3872) J/ orbitally excited B mesons - B c J/ X Cross-sections : - inclusive (1S) differential cross-section - tt production in the lepton+jets, dilepton and all-jets Conclusion and outlooks. - Lots of c/b/t results from DØ channels focus on main spectroscopy / cross-sections results.

3 ISMD 2005I. Ripp-Baudot The Tevatron at Fermilab Run II (since 2001) : s = 1.96 TeV lumi > cm -2 s pb -1 recorded by DØ, 160 to 370 pb -1 analysed : Run I dataset x Main injector & Recycleur Tevatron Chicago p p p 1.96 TeV CDF p DØ integrated luminosity (fbˉ¹) we are here 4 fb -1 8 fb : better than expected ! Design for 2005 Base for 2005

4 ISMD 2005I. Ripp-Baudot The DØ detector Tracking system Calorimeter Muon chambers Muon : excellent coverage | |2.0 + toroïdal magnet Tracking system : 2 T solenoïdal B + 4 layers Silicon + 8 layers Fiber tracker. | |<3.0. Calorimeter : liquid Ar with U/Cu absorber. Small segmentation x + good hermiticity. Coverage | |4.2

5 ISMD 2005I. Ripp-Baudot Heavy Flavour production in DØ Trigger : crucial item ! 3 levels 2.5 MHz 60 Hz B physics : mostly (di)-mu trigger. ~ 3 t t / hours ~ b b / hours - - Considerable increase over the previous datasets. All states accessible : Tevatron is a unique place to study heavy b hadrons (B c, B s, b, B ** ) and the top quark mb 7 pb ~ events / s events / 10 MeV/c 2

6 ISMD 2005I. Ripp-Baudot spectroscopy results

7 ISMD 2005I. Ripp-Baudot Observation of X(3872) by DØ DØ Observation by DØ (PRL 93, , 2004) : data collected apr. 02 jan. 04 ~ 230 pb -1 Using DØ dimuon trigger vertex reconstructed. First observation by Belle in 2003 in J/ + - decay channel. - - Spectroscopic puzzle : D 0 -D *0 hadronic resonance, ccg-hybrids, unknown charmonium state, diquark-antidiquark state, … ? X(3872) J/ ± 100 X(3872) candidates. M(X-J/ ) = ± 3.1 (stat) ± 3.0 (syst) MeV/c 2 At Tevatron : B decay + direct production.

8 ISMD 2005I. Ripp-Baudot Properties of X(3872) DØ p T 15 GeV |y| 1 (2S) with same decay channel = good benchmark for comparison with X(3872). Data separated according to production and decay variables. Conclusion : no significant differences between X(3872) and (2S). l xy 0.01 cm isolation = 1 Helic. 0.4 Future investigations : - Search for radiative decays and other final states with neutrals in progress. - Lifetime measurement. - Search for charge conjugate X + J/ Quantify prompt production w.r.t. through decay in progress. Helicity 0.4 Presented by Belle Summer 2005 : quantum number C=+1 established, X J/ and J/ observed with more than 4 agreement with D 0 D *0 resonance prediction.

9 ISMD 2005I. Ripp-Baudot Reconstruction of orbitally excited B Reconstruction of L=1 B states : the two narrow B **, B 1 and B *, decaying to B (*). DØDØ DØDØ B ± J/ K ± B d J/ K *0 (892)B d J/ K s ± ± ± 41 Precise predictions for B ** properties by HQET interesting lab to test the validity of heavy quark symmetry and help further development of NPQCD. These B hadron candidates + 1 additional track originating from interaction point : B 0 ±, B ±. Exclusively reconstructed B mesons in hadronic decay channels allow measurement of B ** properties. Reconstruction with data collected ~ 350 pb -1 (DØ dimuon triggers). First observation of B 1 and B * as two separate states, with a significance of 7. 2 d ( )( ) ± DØDØ 2 -

10 ISMD 2005I. Ripp-Baudot Study of B ** - Expected decays : Br(B 1 B * ) >> Br(B 1 B ), Br(B * B * ~ Br(B * B ), with B * B distribution of M = M(B ) – M(B) should reveal 3 peaks, but since M(B*) – M(B 1 ) << detector resolution, the first 2 peaks are unresolved. - Expected widths : 1 ~ 2 set 1 = 2 in the fit. 2 2 DØ 2 B * B 2 2 /NDF = 54.3/50 M(B 1 ) = 5724 ± 4 (stat) ± 7 (syst) MeV/c 2 M(B * ) – M(B 1 ) = 23.6 ± 7.7 (stat) ± 3.9 (syst) MeV/c 2 1 = 2 = 23 ± 12 (stat) ± 9 (syst) MeV/c 2 2 Future : increase in stat. will allow the precise measurement of B ** production and decay properties. Fit results : B * B * 2 - Since M(B +** )-M(B 0** ) << mass resolution, B +** ~ B 0** = B **. dd u u B B * 1

11 ISMD 2005I. Ripp-Baudot Observation of B c Heaviest B meson ground state, made of two heavy quarks. Test of heavy quark fragmentation and hadronization. Previously observed by CDF Run I but up to now limited statistics. Reconstructed channel : B c J/ X - 3 muons easy to trigger on. - less background than B c J/ - limited mass precision due to escaping. Using 210 pb -1 of DØ data : 95 ± 12(stat.) ± 11 (syst.) B c signal candidates significance > 5 DØ preleminary Background composition checked with data and MC simulation : 1)Prompt J/ + common vertex with decay-in-flight to, punch- through calo. 2)J/ from B + decay-in-flight to or punch-through in the same jet or elsewhere in event GeV/c 2 )

12 ISMD 2005I. Ripp-Baudot Properties of B c Simultaneous mass/lifetime fit : m Bc = 5.95 (stat ) ± 0.34 (syst ) GeV/c 2 Bc = (stat) ± (syst) ps Under investigation : - establish B c p T spectrum to compare with phenomenological predictions. - smaller systematics errors. - reconstruct exclusive B c J/ heavy flavour background prompt background 5.95 GeV/c 2 Phenomenological predictions : m(B c ) ~ 6.4 GeV/c 2 (B c ) ~ (D meson) ~ 0.3 to 0.5 ps. Mass hypothesis (GeV/c 2 ) -2logL

13 ISMD 2005I. Ripp-Baudot cross-section results

14 ISMD 2005I. Ripp-Baudot Inclusive (1S) differential cross-section DØ measurement (PRL 94, , 2005) : data collected june 2002 sept ~ 159 pb Reconstruction of (1s) + - as function of p T ( ) and in 3 y = ½ ln ranges : 0 < |y | < < |y | < < |y | < 1.8 DØ 4 GeV/c < p T ( ) < 6 GeV/c |y | < < |y | < 1.8 Hypothesis : (1S) are produced unpolarized (CDF Run I measurement). Sensitivity checked < 4 % in all p T bins. new ! E+p z E-p z

15 ISMD 2005I. Ripp-Baudot Inclusive (1S) differential cross-section (cont.) DØ Conclusion : - first measurement in the forward region. - agreement with CDF Run I measurement. - reasonable agreement with theoretical predictions [Berger, Qiu, Wang, PRD 71 (2005)]. - systematics limited : no need to increase stat. up to now. Measurement for |y | < 0.6 : (1S) x Br( (1S) + - ) = 732 ± 19 (stat) ± 73 (syst) ± 48 (lumi) pb new rapidity ranges Future : DØ measurement of (1S) polarization in progress.

16 ISMD 2005I. Ripp-Baudot tt cross-section - Top quark was discovered by CDF and DØ at Tevatron in Largest known mass ( new 2005 : ± 2.9 GeV/c 2 ) and lifetime (~ s) shorter than hadronisation time (~ s) decays as a free quark. At Tevatron, top mainly produced by pair via strong interaction. fully hadronic hadr + jets lepton + jets hadr + jets dilep ton e-e- e+e ud cs ud BR ~ 45 % large statistics - 6 jets - large multijet background with poorly known cross- sections - BR ~ 5 % - 2 jets - clean channel - low statistics no +X analysis so far - BR ~ 30 % - 4 jets - optimum stat/background In all channels : At least 2 bjets possibility to use b-tagging to improve signal/background. all jets -jets -

17 ISMD 2005I. Ripp-Baudot tt cross-section (cont.) - jet multiplicity background control tt measurement one tagged b-jet two tagged b-jets

18 ISMD 2005I. Ripp-Baudot Conclusion and outlooks Studies of beauty and top production are important tests of perturbative QCD. Tevatron is a unique place to study top and several B properties. DØ takes advantage of its muon trigger with excellent coverage, and its new tracking system. It benefits furthermore from the very high statistics provided by the Tevatron : about 200 to 400 pb -1 analysed up to now. Some analysis still limited by stat, but statistics also allow systematics improvements. Already 1 fb -1 delivered, 4-8 fb -1 expected around 2009 lots of good results to come.

19 ISMD 2005I. Ripp-Baudot Backup slides

20 ISMD 2005I. Ripp-Baudot Inclusive -tagged jet cross-section Previous measurements of heavy quark production at the Tevatron showed discrepancies with theoretical predictions, now understood after evolution of both theory and experimental measurements. Focus on b-jets rather than b-quarks directly observable. 294 pb -1 sample of mu-tagged jets in the central region |y| 50 GeV). -tagged jet : have a within the jet cone and the production vertex occurs within a cylinder of r=10 cm centered on the beam axis to get rid of contamination from and K decay. # event in each p T bin = p T Trigger PV jet purity measured 1)missed from B decay p T resolution degradation 2)detector resolution taken into account by unsmearing : observed jet p T true jet p T Consider only the top of the detector to avoid selecting fake muons (punch-through the calorimeter) : less muon detector layers on the bottom because of the detectors support. d dp T

21 ISMD 2005I. Ripp-Baudot Inclusive -tagged jet cross-section (cont.) Systematics : - fraction of heavy flavours (p T independent) - jet energy scale (p T dependant) Future : extract exclusive b fraction. Remove light quarks contribution : use the simulation to determine the fraction of -tagged jets originating from a heavy quark (b or c). DØDØ Comparison to theory predictions : 1)PYTHIA LO approximation 2)NLO calculation for inclusive jet calculation pT dependent fraction of jets that are -tagged (PYTHIA)