1 / 21

Heavy Flavour Production Results from DØ Run II

This presentation by Isabelle Ripp-Baudot from IReS Strasbourg provides a comprehensive overview of the heavy flavour production results from the DØ collaboration's Run II at the Tevatron. The focus is on main spectroscopy and cross-sections results involving X(3872), J/Ψp+p− orbitally excited B mesons, and Bc mesons. The DØ detector system, data analysis methods, and significant observations such as the X(3872) decay channel and properties are discussed in detail. Future investigations in the field of heavy flavour physics at the Tevatron are also highlighted.

finna
Download Presentation

Heavy Flavour Production Results from DØ Run II

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related