The CDF and D0 experiments finalize the analysis of their full statistics
collected in the $p \bar p$ collisions at a center-of-mass energy of $\sqrt{s}
= 1.96$ TeV at the Fermilab Tevatron collider. This paper presents several new
results on the properties of hadrons containing heavy $b$- and $c$-quarks
obtained by both collaborations. These results include the search for the rare
decays $B^0, B^0_s \to \mu^+ \mu^-$ (CDF), the study of CP asymmetry in $B_s
\to J\psi \phi$ decay (CDF, D0), the measurement of the like-sign dimuon charge
asymmetry (D0), the measurement of CP asymmetry in $D^0 \to K^+K^-$ and $D^0
\to \pi^+\pi^-$ decays (CDF), and the new measurement of the $B_s \to
D_s^{(*)+} D_s^{(*)-}$ branching fraction (CDF). Both experiments still expect
to produce more results on the properties of heavy flavours.Comment: Contribution to the XLVIIth Rencontres de Moriond session devoted to
  Electroweak Interactions and Unified Theorie

Borissov, G.

U., /Lancaster

English

arXiv

The CDF and D0 experiments finalize the analysis of their full statistics collected in the p{bar p} collisions at a center-of-mass energy of {radical}s = 1.96 TeV at the Fermilab Tevatron collider. This paper presents several new results on the properties of hadrons containing heavy b- and c-quarks obtained by both collaborations. These results include the search for the rare decays B{sup 0}, B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -} (CDF), the study of CP asymmetry in B{sub s} {yields} J{psi}{phi} decay (CDF, D0), the measurement of the like-sign dimuon charge asymmetry (D0), the measurement of CP asymmetry in D{sup 0} {yields} K{sup +}K{sup -} and D{sup 0} {yields} {pi}{sup +}{pi}{sup -} decays (CDF), and the new measurement of the B{sub s} {yields} D{sub s}{sup (*)+} D{sub s}{sup (*)-} branching fraction (CDF). Both experiments still expect to produce more results on the properties of heavy flavours

UNT Digital Library

HEAVY FLAVOUR RESULTS FROM TEVATRONG. BORISSOV(on behalf of the CDF and DØ collaborations)Department of Physics, Lancaster University,Lancaster LA1 4YB, England, UKThe CDF and DØ experiments finalize the analysis of their full statistics collected in the pp̄collisions at a center-of-mass energy of√s = 1.96 TeV at the Fermilab Tevatron collider.This paper presents several new results on the properties of hadrons containing heavy b-and c-quarks obtained by both collaborations. These results include the search for the raredecays B0, B0s → µ+µ− (CDF), the study of CP asymmetry in Bs → Jψφ decay (CDF, DØ),the measurement of the like-sign dimuon charge asymmetry (DØ), the measurement of CPasymmetry in D0 → K+K− and D0 → π+π− decays (CDF), and the new measurement ofthe Bs → D(∗)+s D(∗)−s branching fraction (CDF). Both experiments still expect to producemore results on the properties of heavy flavours.For past 10 years the Fermilab Tevatron collider has pioneered and established the role ofhadron colliders for flavour physics. It became the main source of results on B0s , Bc mesons,and B baryons. Many crucial measurements, like the mass difference in the B0s system, wereobtained here. Currently the Tevatron experiments finalize their study and publish the resultswith the full statistics up to 10 fb−1.In this paper I review• search for the rare decays B0, B0s → µ+µ− obtained by the CDF collaboration;• study of CP asymmetry in B0s → J/ψφ decay reported by the CDF and DØ collaborations;• updated measurement of the like-sign dimuon charge asymmetry (D0 collaboration);• new measurement of the difference of CP asymmetry in D0 → K+K− and D0 → π+π−decays (CDF collaboration);• measurement of the branching fraction of B0s → Ds(∗)+Ds(∗)− decay (CDF collaboration).The standard model (SM) predicts a very low value for the branching fractions of bothB0 → µ+µ− and B0s → µ+µ− decays. The most recent SM prediction for these fractions is 1Br(B0s → µ+µ−) = (3.2± 0.2)× 10−9,Br(B0 → µ+µ−) = (1.0± 0.1)× 10−10. (1)The contribution of new physics beyond the SM can significantly modify these values, thereforethese rare decays can provide important constraints on various new physics models.FERMILAB-CONF-12-287-EOperated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. 0102030 < 0.76Nν0.70 <  < 0.85Nν0.76 <  < 0.90Nν0.85 <  < 0.94Nν0.90 < -µ+µ→0sB )2 (MeV/cµµm0510155322 5370 5418 5322 5370 5418 5322 5370 5418 5322 5370 5418 < 0.97Nν0.94 <  < 0.987Nν0.97 <  < 0.995Nν0.987 <  > 0.995NνBackground4.1)×+Signal (SM 2Candidates per 24 MeV/cFigure 1: For the Bs mass region, the observed number of events (points) is compared to the total expectedbackground (light grey) and its uncertainty (hatched) for different values of νN . The hashed area representsthe systematic uncertainty on the mean expected background while the error bars on the points represent theassociated poisson uncertainty. Also shown is the expected contribution from B0s → µ+µ− events (dark gray)using a branching fraction that corresponds to the central value from the fit to the data, which is 4.1 times theexpected SM value.The CDF collaboration presented in summer 2011 the analysis 2 with 7 fb−1 featuringan accumulation of signal-like events in the B0s mass region with ∼ 2.5σ deviation from thebackground-only hypothesis. The new CDF analysis presented here includes the full Run2statistics corresponding to 9.6 fb−1. Given the increased interest to the previous result, theanalysis of the remaining statistics is kept the same. The separation between the signal andbackground in this analysis is achieved using the neural network. Figure 1 shows the observedand expected number of events in the B0s → µ+µ− search for the different values of the neu-ral network output variable νN . There is an excess of the signal-like events for νN > 0.97,while the agreement between the observed and expected number of events is very good for thebackground-dominated region νN < 0.97. The p-value of the SM signal plus background hy-pothesis for νn > 0.97 is 7%. The excess of events in the 0.97 < νN < 0.987 bin is not increasedwith the addition of the new statistics and is consistent with the statistical fluctuation. Thep-value of the SM signal plus background hypothesis for two largest νN bins is 22.4%, while thep-value of background only hypothesis is 2.1%. Thus, while still not conclusive, the experimentbecomes sensitive to the SM contribution of B0s → µ+µ− decay and shows a good agreementwith the SM expectation.The results obtained by the CDF collaboration with 9.6 fb−1 are:Br(B0s → µ+µ−) = (1.3+0.9−0.7)× 10−8,Br(B0 → µ+µ−) < 4.6× 10−9 (3.8× 10−9) at 95% (90%) C.L. (2)The CDF collaboration also reports the first double sided limit on Br(B0s → µ+µ−):0.8× 10−9 < Br(B0s → µ+µ−) < 3.4× 10−8 at 95% C.L.,2.2× 10−9 < Br(B0s → µ+µ−) < 3.0× 10−8 at 90% C.L. (3)These results are consistent with other searches of these rare decays.An important part of the research of heavy flavours at hadron colliders is devoted to themeasurement of the CP asymmetry. Among other reasons, the interest to this phenomenonis explained by the fact that the magnitude of the CP asymmetry included in the SM is notsufficient to describe the observed abundance of matter in our universe 3, which implies that [rad]φψJ/sφ-3 -2 -1 0 1 2 3]-1 [pssΓ∆-0.6-0.4-0.200.20.40.6-1CDF Run II Preliminary L = 9.6 fb A. Lenz and U. Nierste, arXiv:1102.4274v1 (2011)1-1 0.021) ps±|= (0.087 12Γ 2|268% CL  95% CL 1SM expectationSymmetry line2Mixing Induced CP ViolationSM p-value = 29.8%−1 0.12 ps± 17.77 ≡ sM∆SM68% CL90% CL95% CL−3 −2 −1 2 30 1−0.4−0.3−0.2−0.100.10.20.30.4 −1D    Run II, 8 fb (rad)φψJ/sφ)−1 (pssΓ∆Figure 2: Confidence regions in φJ/ψφ − ∆Γs plane. Left plot: the measurement of CFT collaboration. Thesolid (blue) and dot-dashed (red) contours show the 68% and 95% confidence regions, respectively. The shaded(green) band is the theoretical prediction of mixing-induced CP asymmetry. Right plot: the measurement of DØcollaboration. Two-dimensional 68%, 90% and 95% C.L. contours including systematic uncertainties are shown.The standard model expectation is indicated as a point with an error.some additional sources of CP asymmetry should exist. They could reveal themselves by thedeviation of the observed CP asymmetry from the SM prediction.One of the most promising channels to search for the new sources of CP asymmetry is thedecay B0s → J/ψφ. The CP asymmetry in this decay is described by the phase φJ/ψφ. Withinthe SM, this phase is related with the angle βs of the (bs) unitarity triangle and is predicted tobe very small 4:φJ/ψφ(SM) = −2βs = −0.38± 0.02. (4)This phase can be significantly modified by the new physics contribution and this deviation fromthe SM can be detected experimentally.Both CDF and DØ experiments report the new study of B0s → J/ψφ decay with the fullstatistics. The CDF collaboration reconstructs about 11000 these decays using the integratedluminosity 9.6 fb−1. The new analysis5 is similar to the previous measurement with a part of thestatistics 6. The result of this analysis is presented in Fig. 2(left plot) as the confidence regionsin φJ/ψφ −∆Γs plane. It can be seen that the obtained confidence region is consistent with theSM prediction within 1σ. The obtained confidence regions for the quantity βJ/ψφs ≡ −φJ/ψφ/2isβJ/ψφs ∈ [−π/2,−1.51] ∪ [−0.06, 0.30] ∪ [1.26, π/2] at 68% C.L.βJ/ψφs ∈ [−π/2,−1.36] ∪ [−0.21, 0.53] ∪ [1.04, π/2] at 95% C.L. (5)A similar analysis of B0s → J/ψφ decay by the DØ collaboration 7 is based on 6500 signalevents collected using the integrated luminosity 8 fb−1. The result of this analysis is shown inFig. 2 (right plot). The obtained confidence region is consistent with the SM prediction, andthe p-value for the SM point is 29.8%. The following values are obtained in this analysis:τs = 1.443+0.038−0.035 ps,∆Γs = 0.163+0.065−0.064 ps−1,φJ/ψφ = −0.55+0.38−0.36. (6)-0.04-0.0200.02-0.04 -0.02 0 0.02SMDØ, 9.0 fb-1A bsl(IP<120 )Absl (IP>120 )A bsl68%C.L.95%C.L.68% and 95% C.L. regionsare obtained fromthe measurements withIP selectionsadslas slFigure 3: Measurement of Absl with different muon IP selections in the (adsl, assl) plane. The bands represent the±1 standard deviation uncertainties on each individual measurement. The ellipses represent 68% and 95% two-dimensional CL regions, respectively, of of adsl and assl values obtained from the measurements with IP selections.Another quantity sensitive to the new sources of the CP asymmetry is the like-sign dimuoncharge asymmetry, which is defined asAbsl ≡N++b −N−−bN++b + N−−b. (7)Here N++b and N−−b represent the number of events containing two b hadrons decaying semilep-tonically and producing two positive or two negative muons, respectively. The non-zero value ofthe asymmetry Absl signals the presence of the CP violation in mixing in the semileptonic decaysof neutral B mesons. The standard model predicts a very small value compared to the currentexperimental sensitivity. Recently the DØ collaboration released the new measurement of thisquantity 8 using the integrated luminosity 9 fb−1. The obtained value of Absl deviates from theSM prediction by 3.9 σ:Absl = (−0.787± 0.172± 0.093)% (8)The asymmetry Absl contains the contribution from the semileptonic charge asymmetries adsland assl of B0 and B0s mesons, respectively. The analysis of the dependence of Absl on the muonimpact parameter (IP) allows to obtain the separate values of adsl and assl:adsl = (−0.12± 0.52)%,assl = (−1.81± 1.06)%. (9)The precision of these quantities is comparable with the available world average measurements.Figure 3 presents the results of the IP study in the (adsl, assl) plane together with the result (8) ofthe Absl measurement. The ellipses represent the 68% and 95% two-dimensional confidence level(CL) regions, respectively, of adsl and assl values obtained from the IP study. The obtained valuesof adsl and assl are in a good agreement with the independent measurement of assl by the DØcollaboration 9, and the world-average value of adsl reported by the HFAG10. The discrepancybetween the measured value of Absl and the SM prediction requires an independent confirmation.One more promising channel to search for the new sources of CP asymmetry is the singleCabbibo suppressed decays D0 → K+K− and D0 → π+π−. Although the exact theoreticalprediction of CP asymmetry in these decays is difficult to obtain due to the non-perturbativecontributions, the CP asymmetry at O(1%) level could signal the contribution of new physics.]2-mass [GeV/csπ0Invariant D2.005 2.01 2.015 2.022Candidates per 0.1 MeV/c02040310×/ndf = 394/2992χ 1265±) = 590874 +sπ) -K+ K→ (0 D→ +N(D*)-1Data (9.7 fbFitMultibody D decaysRandom pionsσ/∆-202]2-mass [GeV/csπ0Invariant D2.005 2.01 2.015 2.022Candidates per 0.1 MeV/c05101520310×/ndf = 368/3082χ 590±) = 269871 +sπ) -π+π → (0 D→ +N(D*)-1Data (9.7 fbFitRandom pionsσ/∆-4-202Figure 4: Projections of the combined fit on data for tagged D0 → K+K− (left) and D0 → π+π− (right) decays.The CDF collaboration previously measured11 the separate values of asymmetries ACP (K+K−)and ACP (π+π−) with 6 fb−1:ACP (π+π−) = (+0.22± 0.24± 0.11)%,ACP (K+K−) = (−0.24± 0.22± 0.09)%. (10)The new analysis 12 uses the full data set corresponding to the luminosity 9.6 fb−1 and isoptimized for the measurement of ∆ACP ≡ ACP (K+K−)−ACP (π+π−). It is motivated by therecent result reported by the LHCb experiment 13:∆ACP (LHCb) = (−0.82± 0.21± 0.11)%. (11)Many systematic uncertainties cancel in the difference of asymmetries and therefore theselection cuts in the new CDF analysis are loosened to increase the statistics. In total 550KD0 → π+π− decays and 1.21M D0 → K+K− decays are selected. Both decays are reconstructedin the decays D∗± →(−)D0 π±. Figure 4 shows the mass distributions of the the reconstructedD0 → K+K− and D0 → π+π− decays. It can be seen that the quality of the description of thedata is excellent. Using the collected statistics, the CDF collaboration obtains∆ACP (CDF) = (−0.62± 0.21± 0.10)%, (12)which corresponds to 2.7 σ deviation from zero. This result is consistent with the LHCb mea-surement (11). The combination of the CDF and LHCb results gives ∼ 3.8σ deviation of ∆ACPfrom zero.The CDF collaboration reports 14 one more interesting result on the properties of B0s meson,namely the measurement of the branching fraction Br(B0s → D(∗)+s D(∗)−s ). It is obtained usingthe semi-exclusive decay modesB0s → D+s D−s ,B0s → D∗+s D−s + D+s D∗−s ,B0s → D∗+s D∗−s , (13)with Ds → φπ or Ds → K∗K. The resulting invariant mass distribution is presented in Fig. 5.In total 750 signal events in these decay modes are reconstructed. Using this statistics, the5.0 5.510203040 )-πφ(-s) D+πφ(+sD DataFit projectionBackground-s D+s D→ s0B-s D+*s D→ s0B-*s D+*s D→ s0BCDF II Preliminary -16.8 fbInvariant Mass (GeV/c²)5.0 5.50204060)-πφ(-s) D+K0*K(+sD - D+s D→ 0B- D*+s D→ 0B- D+*s D→ 0B- D*+*s D→ 0B2Candidates per 10 MeV/cFigure 5: Invariant mass distribution of B0s → D+s (φπ+)D−s (φπ−) and B0s → D+s (K∗0K+)D−s (φπ−).following result is obtainedBr(B0s → D+s D−s ) = (0.49± 0, 06± 0.05± 0.08)%,Br(B0s → D∗+s D−s + D+s D∗−s ) = (1.13± 0.12± 0.09± 0.19)%,Br(B0s → D∗+s D∗−s ) = (1.75± 0.19± 0.17± 0.29)%. (14)The total branching fraction of these decay modes is found to beBr(B0s → D(∗)+s D(∗)−s ) = (3.38± 0.25± 0.30± 0.56)%. (15)In conclusion, the experiments at the Tevatron finalize the analysis of their full statistics.This paper presents the new results obtained in the search for the rare decays B0, B0s → µ+µ−(CDF), the study of CP asymmetry in Bs → Jψφ decay (CDF, DØ), the measurement of thelike-sign dimuon charge asymmetry (DØ), the measurement of CP asymmetry in D0 → K+K−and D0 → π+π− decays (CDF), and the new measurement of the Bs → D(∗)+s D(∗)−s branchingfraction (CDF). Many more exciting results from the DØ and CDF experiments with the fullstatistics can be expected soon.References1. A. Buras et al, JHEP 1009, 106 (2010).2. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. Lett. 107, 191801 (2011).3. P. Huet and E. Sather, Phys. Rev. D 51, 379 (1995).4. A. Lenz and U. Nierste, arXiv:1102.4274 (2011).5. The CDF collaboration, CDF public note 10778 (2012).6. T. Aaltonen et al. (CDF Collaboration), arXiv:1112.1726 2011.7. V.M. Abazov et al. (DØ Collaboration), Phys. Rev. D 85, 032006 (2012).8. V.M. Abazov et al. (DØ Collaboration), Phys. Rev. D 82, 032001 (2010),V.M. Abazov et al. (DØ Collaboration), Phys. Rev. D 84, 052007 (2011).9. V.M. Abazov et al. (DØ Collaboration), Phys. Rev. D 82, 012003 (2010).10. D. Asner et al., Heavy Flavour Averaging Group (HFAG), arXiv:1010.1589 (2010).11. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. D 85, 012009 (2012).12. The CDF collaboration, CDF public note 10784 (2012).13. R. Aaij et al. (LHCB Collaboration), Phys. Rev. Lett. 108, 111602 (2012).14. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. Lett. 108, 201801 (2012).

Heavy Flavour results from Tevatron

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Heavy Flavour results from Tevatron

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