CDF recent results Paolo Mastrandrea (INFN Roma) on behalf of the CDF Collaboration

Transcription

1 CDF recent results Paolo Mastrandrea (INFN Roma) on behalf of the CDF Collaboration Società Italiana di Fisica - XCVII Congresso Nazionale - L'Aquila, Settembre, 2011 SIF 2011, L'Aquila September Paolo Mastrandrea 1

2 CDF experiment Wide international collaboration (~600 physicists); Very rich physics program studying processes over ~10 orders of magnitude in cross-section: heavy flavour physics; properties of W and Z bosons; properties of the top quark; search for the Higgs boson; search of processes beyond the Standard Model; Very rich record of publications; A selection of recent results is presented in this talk; For a complete record: SIF 2011, L'Aquila September Paolo Mastrandrea 2

3 Tevatron Initial luminosity record cm -2 s -1 3 May 2011 p-p s = 1.96 TeV 6.28 km circumference 2 interaction point: CDF, DØ Initial Luminosity 43%+ design Integrated luminosity ~ 12 fb -1 delivered per experiment ~ 12 fb -1 (on tape ~ 10 fb -1 ) reached ~ 2 fb -1 per year running stable at high luminosity Presented results up to 8.6 fb -1 SIF 2011, L'Aquila September Paolo Mastrandrea 3

4 CDF detector Multipurpose detector; Large radius drift chamber (1.4m); 1.4T solenoid; Projective calorimeters; Muon chambers; Silicon Vertex Detector; SVT: online high precision L2 based on original associative memory application. Muon system Had calorimeter EM calorimeter Solenoid Tracker Silicon Vertex Detector SIF 2011, L'Aquila September Paolo Mastrandrea 4

5 CDF results Heavy flavour physics Properties of W and Z bosons Properties of the top quark Search of processes beyond the Standard Model Search for the Higgs boson SIF 2011, L'Aquila September Paolo Mastrandrea 5

6 X b 0 observation 4.2 fb -1 X b 0 first observation; X b - first observation in this channel; Complete reconstruction of the full decay chain; Complex hadronic final states; No leptons for trigger; Events acquired with the displaced track trigger (SVT) Mass [MeV/c 2 ] X b ± 5.1 ± 1.4 X b ± 5.0 ± 1.3 arxiv: v1 SIF 2011, L'Aquila September Paolo Mastrandrea 6

7 B s /B 0 m + m fb -1 FCNC processes that can occur in the SM through higher order loop diagrams; Enanched NN signal-to-background discriminant (n N ); B 0 data are consistent with background expectations - world s most stringent upper limit on BR; B s 0 data are in excess of the background prediction with a p-value of 0.27% BR(B 0 mm) < 6.0 x 95% CL 4.6 x 10-9 < BR(B s0 mm) < 3.9 x 90% CL BR(B s0 mm) = ( ) x 10-8 arxiv: SIF 2011, L'Aquila September Paolo Mastrandrea 7

8 Charmless decays of neutral b mesons 6.1 fb -1 First evidence of B s0 p + p - (significance 3.7s); World's best limit on BR(B s0 K + K - ); Tests accuracy of effective model of strong interactions; Decay rates sensible to new physics; Hadronic trigger (SVT). BR(B s0 p + p - ) = (0.57 ± 0.15 (stat) ± 0.10 (syst)) x 10-6 CDF Public note x 10-6 < BR(B s0 K + K - ) < 0.46 x 90% CL SIF 2011, L'Aquila September Paolo Mastrandrea 8

9 Z+b 7.9 fb -1 Precise test of the QCD; Main background for ZH llbb search; Test/validation of MC generators; NN used to improve muon ID (30% gain); b fraction extracted by a fit to secondary vertex mass distribution; CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 9

10 ZZ 4l 6.1 fb -1 Precise test of the Electroweak sector; ZZ is the last diboson channel without a precise cross-section measurement; l ± = e ±, m ± ; Observed: 14 events; Expected: 10.4 signal background; Measured crosssection in agreement with NLO prediction of 1.4 pb s(pp ZZ) x BR(ZZ 4l) = 2.18 ± 0.63 (stat.) ± 0.30 (syst.) pb CDF Note SIF 2011, L'Aquila September Paolo Mastrandrea 10

11 ZZ llnn 5.9 fb -1 Cut based selection of ll+me T Background due mainly to detector resolution and jet mismeasurement; NN discriminant; NN output fitted with MC templates to extract ZZ component. s(pp ZZ) = (stat.) (syst.) pb CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 11

12 ZZ - Search for high-mass resonances 6.0 fb -1 4 events in ZZ 4l channel have invariant masses consistent with 327 GeV/c 2 ; Analysis in the ZZ llnn and ZZ lljj channels do not confirm a heavy resonance decaying into a pair of Z bosons; Upper limits set for 2 signal models. s(pp X ZZ) < 0.26 (0.28) 95 % CL CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 12

13 WZ 7.1 fb -1 Crucial background for the H WW search in the associated production; Three-lepton + missing E T signature; NN discriminant; Fit to Z p T distribution to extract TGC limits. s(wz) = (stat) (sys) pb s th (WZ) = 3.46 ± 0.21 pb CDF Public note 10176, SIF 2011, L'Aquila September Paolo Mastrandrea 13

14 W+jj 7.3 fb -1 Invariant mass distribution of jet pairs produced in association with a W; Analysis updated from 4.3pb -1 to 7.3pb -1 ; The significance of the excess increases from 3.2 to 4.1 standard deviations, consistent with expectation from the increase in the data sample size Phys.Rev.Lett.106:171801, SIF 2011, L'Aquila September Paolo Mastrandrea 14

15 Evidence for WW/WZ ln+hf 7.5 fb -1 Ideal channel to validate Higgs analysis techniques; p-value s excess; Multivariate discriminant based on the Support Vector Machine algorithm used to reduce QCD background. (s x BR) / (s x BR) SM = CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 15

16 ZZ/ZW lljj 6.6 fb -1 Z reconstructed in charged leptons decay; A quark-gluon NN discriminant quantizes the spatial spread of the energy and track momenta contained within a jet; NN output used to correct the background modeling. s (ZZ+WZ) < % CL (1.3 x s SM ) CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 16

17 Forward backward asymmetry of top quark 5.3 fb -1 Combination of di-lepton and lepton plus jet measurements CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 17

18 W polarization in Top dilepton events 5.1 fb -1 W boson polarizations are determined by a comparison of angular distribution of leptons in W rest-frame (cos q * ) with the templates corresponding to left-handed, right handed and longitudinal fractions exclusively; Model independent measurement. Observed SM f (stat.) ± 0.06 (syst.) 0.7 f ± 0.09 (stat.) ± 0.03 (syst.) 0.0 CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 18

19 Top in hadronic t + jets 2.2 fb -1 First measurement of the top quark mass in the hadronic t + jets channel; NN removes most of the QCD background; Matrix element techniques used to measure top mass. M t = ± 9.3 (stat.) ± 3.7 (syst.) GeV/c 2 s(tt) = 8.8 ± 3.3 (stat.) ± 2.7 (syst.) pb CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 19

20 Top CDF 5.8 fb -1 CDF Public note M t = ± 0.6 (stat.) ± 0.9 (syst.) GeV/c 2 SIF 2011, L'Aquila September Paolo Mastrandrea 20

21 m W [GeV] Top Tevatron 5.8 fb -1 m t [GeV] arxiv: M t = ± 0.9 GeV/c 2 < 1 GeV/c 2 SIF 2011, L'Aquila September Paolo Mastrandrea 21

22 H gg 7.0 fb -1 Extended photon selection: Forward photons included; Additional central photon categories; new algorithm which selects central photons that have converted into an e + e - pair; NN to reject jet background; 33% improvement respect to 5.4 fb -1 result; Observed limit at 120 GeV/c 2 is <2s when trial factor is taken into account. CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 22

23 WH lnbb 7.5 fb -1 Evenst selected with: 1 charged lepton; large missing E T ; 2 jets; 1 b-tagged jet; 3 taggers used (Sec. Vertex, JetProb, NNbased); NN discriminant to improve signal to background separation; Combination with independent analysis for events with 3 jets. CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 23

24 H 4l 8.2 fb -1 4e, 4m and 2e2m final states; Some acceptance from ZH ZWW; 8 observed events, consistent with no events from Higgs boson decay. CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 24

25 H WW * 8.2 fb -1 Search for SM H WW * decay in dilepton and tri-lepton plus missing E T final states; Increased signal acceptance: events with low dilepton invariant mass; consider also associated production with a W or a Z boson via vector boson fusion; 3 NN separately trained to distinguish signal from background in final states with 0, 1, 2 jets. Observed exclusion [ 156 ; 175 ] GeV/c 95% CL CDF only CDF Public note SIF 2011, L'Aquila September Paolo Mastrandrea 25

26 CDF 8.2 fb channels considered; ~70 measuremets combined. Observed exclusion [ ; ] GeV/c 2 [ ; ] GeV/c 95% CL SIF 2011, L'Aquila September Paolo Mastrandrea 26

27 Tevatron 8.6 fb -1 CDF + D0 combination. Observed exclusion [ 100 ; 108 ] GeV/c 2 [ 156 ; 177 ] GeV/c 95% CL arxiv: v2 SIF 2011, L'Aquila September Paolo Mastrandrea 27

28 Higgs analyses perspectives CDF analyses are improving faster than just integrated luminosity gain for both low and high mass Higgs searches. SIF 2011, L'Aquila September Paolo Mastrandrea 28

29 CDF Run II End of Data Taking - 30/9/2011 SIF 2011, L'Aquila September Paolo Mastrandrea 29

30 Conclusion CDF has deliverd a rich and exciting research program; Deep understanding of the experimental apparatus; Maturity of the analysis techniques; >20% more statistics still to be analysed; Pushing to get the best possible measurements delivered before the changeover! SIF SIF 2011, 2011, L'Aquila September Paolo Mastrandrea 30

31 Backup x.x fb -1 reference SIF 2011, L'Aquila September Paolo Mastrandrea 31

32 FCNC decay L b0 Lm + m fb -1 b smm processes occur in SM through higher order amplitudes; several BSM theories provide enanched rates for these decays; First observation of FCNC L b0 Lm + m - with a statistical significance of 5.8 s Differential branching ratio measurement for L b0 Lm + m - and B b0 fm + m - b smm process measured in several final states. resonant charmonium arxiv: SIF 2011, L'Aquila September Paolo Mastrandrea 32

33 FCNC decay B K (*) m + m - - angular distributions 6.8 fb -1 World most precise A FB measurement; Competitive with Bells's measurement; No discrepancy with SM predictions. resonant charmonium arxiv: F L longitudinal polarization fraction A (2) T transverse polarization asymmetry A FB A im foreward-backward asymmetry time-reversal-odd charge-and-parity asymmetry SIF 2011, L'Aquila September Paolo Mastrandrea 33

34 Dark matter search with top 5.7 fb -1 Dark matter search at collider; Search for an exotic 4th generation quark T' decaying to t+x, where X is a dark matter candidate; m X 70 GeV/c 2 for m T' = 400 GeV/c 95% CL arxiv: v1 SIF 2011, L'Aquila September Paolo Mastrandrea 34