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Heavy flavour production results from DØ Run II

This presentation outlines key high-energy physics results from the DØ experiment at the Tevatron collider, including spectroscopy, cross-sections, and detector capabilities. Focus on X(3872) and B mesons. Strong emphasis on heavy b hadron studies and top quark properties.

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Heavy flavour production results from DØ Run II

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  1. 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 I. Ripp-Baudot

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

  3. Chicago  Design for 2005 The Tevatron at Fermilab p p 2005: better than expected ! Base for 2005 1.96 TeV DØ 2004 p CDF 2003 Tevatron p 2002 Main injector & Recycleur integrated luminosity (fbˉ¹) 8 fb-1 Run II (since 2001) : √s = 1.96 TeV lumi > 1032 cm-2s-1 800 pb-1 recorded by DØ, 160 to 370 pb-1 analysed. 2009 : Run I dataset x 40-80 we are here 4 fb-1 2005 2007 2009 I. Ripp-Baudot

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

  5. Considerable increase over the previous datasets.All states accessible : Tevatron is a unique place to study heavy b hadrons (Bc, Bs, Lb, B**) and the top quark. Heavy Flavour production in DØ 0 Trigger : crucial item ! 3 levels 2.5 MHz 60 Hz B physics : mostly (di)-mu trigger. 70 mb ~ 7.106 events / s ~ 20.106 b b / hours - - 7 pb ~ 3 t t / hours events / 10 MeV/c2 I. Ripp-Baudot

  6. spectroscopyresults I. Ripp-Baudot

  7. First observation by Belle in 2003 in J/Yp+p- decay channel. Observation of X(3872) by DØ - Spectroscopic puzzle: D0-D*0 hadronic resonance, ccg-hybrids, unknown charmonium state, diquark-antidiquark state, … ? - DØ Observation by DØ (PRL 93, 162002, 2004) : data collected apr. 02  jan. 04~ 230 pb-1 Using DØ dimuon trigger. m+ m- p+ p-vertex reconstructed. X(3872)  J/yp+p- 522 ± 100 X(3872) candidates. DM(X-J/y) = 774.9 ± 3.1(stat) ± 3.0(syst) MeV/c2 At Tevatron :B decay + direct production. I. Ripp-Baudot

  8. y(2S) with same decay channel = good benchmark for comparison with X(3872). Data separated according toproduction and decay variables. Properties of X(3872) Conclusion :no significant differences between X(3872) and y(2S). DØ |y| ‹ 1 pT › 15 GeV • Future investigations : • - Search for radiative decays and other final states with neutrals  in progress. • - Lifetime measurement. • Search for charge conjugate X+  J/yp+p0 • Quantify prompt production w.r.t. through decay  in progress. isolation = 1 Helic.mm ‹ 0.4 Helicitypp ‹ 0.4 Dlxy ‹ 0.01 cm Presented by Belle Summer 2005 : quantum number C=+1 established, X  g J/y and p+p-p0 J/y observed with more than 4s  agreement with D0D*0 resonance prediction. I. Ripp-Baudot

  9. Reconstruction ofL=1 B states: the two narrow B**,B1 and B*, decaying toB(*)p. Reconstruction of orbitally excited B 2 Precise predictionsfor B** properties by HQET  interesting lab to test the validity of heavy quark symmetry and help further development of NPQCD. Exclusively reconstructed B mesons in hadronic decay channels allow measurement of B** properties. Reconstruction with data collected 2002  2004 ~ 350 pb-1 (DØ dimuon triggers). DØ DØ DØ B± J/Y K± Bd J/Y K*0(892) Bd J/Y Ks0 2826 ± 93 624 ± 41 7217 ± 127 () - These B hadron candidates + 1 additional track originating from interaction point : B0p±, B±p. ± d • First observation of B1 and B* as two separate states, with a significance of 7s. 2 I. Ripp-Baudot

  10. - Since M(B+**)-M(B0**) << mass resolution, B+**~ B0** = B**. u Study of B** d u d • Expected decays : Br(B1  B*p) >> Br(B1  B p),Br(B*  B*p) ~ Br(B*  B p),with B*  B g  distribution of DM = M(Bp) – M(B) should reveal3 peaks, but sinceM(B*) – M(B1) << detector resolution, the first 2 peaks are unresolved. • - Expected widths : G1 ~ G2  setG1 = G2in the fit. 2 2 2 M(B1) = 5724 ± 4(stat)± 7(syst)MeV/c2 M(B*) – M(B1) = 23.6 ± 7.7(stat)± 3.9(syst)MeV/c2 G1 = G2 = 23 ± 12(stat)± 9(syst)MeV/c2 Fit results : 2 c2/NDF = 54.3/50 DØ Future :increase in stat. will allow the precise measurement of B** production and decay properties. B  B*p 1 B*  B p 2 B*  B*p 2 I. Ripp-Baudot

  11. 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 :Bc J/ymn X - 3 muons  easy to trigger on. - less background than Bc  J/yp - limited mass precision due to escaping n. Observation of Bc   Using 210 pb-1of DØ data :95 ± 12(stat.) ± 11 (syst.) Bc signal candidates significance > 5s • Background composition checked with data and MC simulation : • Prompt J/y+ common vertex with decay-in-flight to m, punch-through calo. • J/y from B+ decay-in-flight to m or punch-through in the same jet or elsewhere in event. DØ preleminary (@ 5.95 GeV/c2) I. Ripp-Baudot

  12. -2logL Properties of Bc signal @ 5.95 GeV/c2 prompt background heavy flavour background Mass hypothesis (GeV/c2) Simultaneous mass/lifetime fit : +0.14 Phenomenological predictions : m(Bc) ~ 6.4 GeV/c2 t(Bc) ~ t(D meson) ~ 0.3 to 0.5 ps. mBc = 5.95(stat)± 0.34(syst)GeV/c2 tBc = 0.448(stat)± 0.121(syst) ps -0.13 +0.123 -0.096 Under investigation :-establish Bc pT spectrum to compare with phenomenological predictions. - smaller systematics errors. - reconstruct exclusive Bc J/y p I. Ripp-Baudot

  13. cross-sectionresults I. Ripp-Baudot

  14. Inclusive U(1S) differential cross-section 4 GeV/c < pT(U) < 6 GeV/c DØ measurement (PRL 94, 232001, 2005) : data collected june 2002  sept. 2003 ~159 pb-1. - Reconstruction of U(1s)  m+m- as function of pT(U) and in 3 y = ½ ln ranges : 0 < |yU| < 0.6 0.6 < |yU| < 1.2 1.2 < |yU| < 1.8 |yU| < 0.6 DØ E+pz E-pz new ! DØ 1.2 < |yU| < 1.8 Hypothesis :U(1S) are produced unpolarized (CDF Run I measurement). Sensitivity checked < 4 % in all pT bins. I. Ripp-Baudot

  15. Inclusive U(1S) differential cross-section (cont.) new rapidity ranges Measurement for |yU| < 0.6 : sU(1S) x Br(U(1S)m+m-) = 732 ± 19(stat) ± 73(syst) ± 48(lumi) pb • 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. DØ Future :DØ measurement of U(1S) polarization in progress. I. Ripp-Baudot

  16. - Top quark was discovered by CDF and DØ at Tevatron in 1995. Largest known mass ( new 2005 :172.7 ± 2.9 GeV/c2) and lifetime (~ 5.10-25 s) shorter than hadronisation time (~ 10-23 s)  decays as afree quark. At Tevatron, top mainly produced by pair via strong interaction. tt cross-section • BR ~ 30 % • 4 jets • optimum stat/background ℓ-jets - cs - BR ~ 45 %  large statistics - 6 jets - large multijet background with poorly known cross-sections thadr + jets - fully hadronic lepton + jets all jets - ud no t+X analysis so far - t- thadr + jets t + ℓ t t - m- • - BR ~ 5 % • 2 jets • clean channel • low statistics ℓ-ℓ dilepton - t + ℓ lepton + jets e- In all channels : At least 2 bjets possibility to use b-tagging to improve signal/background. - - - - - m+ t+ - e+ ud cs I. Ripp-Baudot

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

  18. 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. I. Ripp-Baudot

  19. Backup slides I. Ripp-Baudot

  20. Previous measurements of heavy quark production at the Tevatron showeddiscrepancieswith theoretical predictions,now understood after evolution of both theory and experimental measurements. Focus onb-jetsrather than b-quarks directly observable. 294 pb-1 sample of mu-tagged jets in the central region |y| < 0.5  differential cross-section as a function ofjet ET. Very high jet Et(> 50 GeV). m-tagged jet :have a m within the jet cone and the m production vertex occurs within a cylinder of r=10 cm centered on the beam axis  to get rid of m contamination from p and K decay. Inclusive m-tagged jet cross-section Consider only thetop of the detectorto avoid selecting fake muons (punch-through the calorimeter) : less muon detector layers on the bottom because of the detector’s support. measured dsm eTriggerePVejetem # event in each pT bin =  DpT dpT purity • missed n from B decay  pT resolution degradation • detector resolution taken into account by unsmearing : observed jet pT true jet pT I. Ripp-Baudot

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

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