Recent B Physics Results and Silicon Detector Longevity Studies from CDF

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1 Recent B Physics Results and Silicon Detector Longevity Studies from CDF

2 Contents CDF Silicon Detectors: Preparedness for the proposed Run III Radiation ageing of the sensors Recent B Physics Results: B hadron lifetimes Spectroscopy Summary 11/23/10 S. Behari, CDF Results, TIFR 2

3 CDF Run II Detector at Tevatron 11/23/10 S. Behari, CDF Results, TIFR 3

Running beyond 2011? (Run III) The Tevatron is going strong: ~100 publications last year alone. LHC 2010/11 plan: 1 fb -1 @ 7 TeV by the end of 2011 & down in 2012 for 1-1.

4 Running beyond 2011? (Run III) The Tevatron is going strong: ~100 publications last year alone. LHC 2010/11 plan: 1 fb 7 TeV by the end of 2011 & down in 2012 for yrs Tevatron will remain highly competitive in a variety of physics programs, especially including the low mass SM Higgs searches Strong case to run 3 more years (20 fb -1 ) HIGGS REACH Last month the P5 panel recommended DoE to go ahead if it can provide an additional $35M/yr to run the Tevatron. Analyzed Lum/Exp (fb -1 ) 2 x CDF Projections MH (GeV) With projected improvements achieved (x1.5 in sensitivity from now) Expected sensitivity 11/23/10 S. Behari, CDF Results, TIFR 4

5 CDF II Silicon Detectors 11/23/10 S. Behari, CDF Results, TIFR 5

6 Radiation Damage Two general types of radiation damage to the sensors: 11/23/10 S. Behari, CDF Results, TIFR 6

7 Aging Studies Variables of Interest 11/23/10 S. Behari, CDF Results, TIFR 7

Radiation Field In CDF Collision Hall Measured using more than 1000 thermo-luminescent dosimeters (TLDs) Two different data-taking periods allowed for distinction between fields:

8 Radiation Field In CDF Collision Hall Measured using more than 1000 thermo-luminescent dosimeters (TLDs) Two different data-taking periods allowed for distinction between fields: due to beam losses due to pp collisions p p (See R. J. Tesarek et al., IEEE NSS 2003) Radiation field is collision-dominated and scales with 11/23/10 S. Behari, CDF Results, TIFR 8

9 Evolution of Bias Currents α dam is constant for several orders of fluence The fluence integrated luminosity relationship depends on distance of the sensor to the beam 11/23/10 S. Behari, CDF Results, TIFR 9

10 Depletion Voltage Evolution Depletion voltage is the bias voltage required to get rid of free carriers in the bulk of the detector. The expected evolution depends on the dose (Hamburg Model): Before type inversion the depletion voltage decreases due to the reduction in the amount of free carriers After type inversion, depletion voltage steadily increases. 11/23/10 S. Behari, CDF Results, TIFR 10

11 Depletion Voltage Measurement 11/23/10 S. Behari, CDF Results, TIFR 11

12 Depletion Voltage Study -- Signal Vs. Bias Plot MPV (Most Probable Value) of charge for different bias voltages Define depletion voltage, V d, as voltage that collects 95% of the charge at the plateau Depletion Voltage as a function of integrated luminosity 3 rd order polynomial fit around the inversion point Linear fit to extrapolate to the future 11/23/10 S. Behari, CDF Results, TIFR 12

13 Depletion Voltage Projection L00-L0 We will be able to fully deplete most of the sensors until 11 fb -1 11/23/10 S. Behari, CDF Results, TIFR 13

14 Depletion Voltage Projection - L1 Then, are the outer layers of no concern? Some were found underdepleted and were recovered by adjusting their V dep. 11/23/10 S. Behari, CDF Results, TIFR 14

Red circles indicate wedges, where all ladders are dead. Blue circles indicate L0-only dead.

15 How does a degraded L0 impact b-tagging? Plot depicts b-tagging efficiency in data, for jets classified by which SVX L0 wedge they are aimed at. Red circles indicate wedges, where all ladders are dead. Blue circles indicate L0-only dead. Constant is fit to efficiencies for wedges by bulkhead, excluding red and blue circled wedges. Conservatively find a drop in b-tagging efficiency not more than 20%. SM Higgs Sensitivity impact 11/23/10 S. Behari, CDF Results, TIFR 15

16 SVXII Signal / Noise Projection Signal from J/ψ µ + µ - tracks strip cluster charge, Noise estimation from regular calibrations 11/23/10 S. Behari, CDF Results, TIFR 16

Leaving NO Ladder Behind Detectors were designed for Run IIa (2-3 fb -1 ) We use almost every opportunity for diagnostic and repair work Currently ~90% ladders integrated, ~80% good (< 1% error

17 Leaving NO Ladder Behind Detectors were designed for Run IIa (2-3 fb -1 ) We use almost every opportunity for diagnostic and repair work Currently ~90% ladders integrated, ~80% good (< 1% error rate), ~10% bad with an average error rate of 10% Overall 2-3% drop after 9 long years of running! A ladder is the smallest detector building block comprised of 2-4 sensors, 4-16 readout chips and read out via a High Density Interconnect (HDI) 11/23/10 S. Behari, CDF Results, TIFR 17

18 Actions Taken to Maximize Longevity 11/23/10 S. Behari, CDF Results, TIFR 18

19 Recent B Physics Results 11/23/10 S. Behari, CDF Results, TIFR 19

20 B Production at Tevatron q b g b g b b g b b q Flavor Creation (annihilation) b g Flavor Creation (gluon fusion) b q Flavor Excitation q g Gluon Splitting g Tevatron is a source of all B-hadron species, B d, B u, B c, B s and Λ b σ b = 29.4 ± 0.6 ± 6.2 µb ( η < 1) (CDF) Huge cross-sections compared to the the B-factories but proportionally large backgrounds as well Since σ(bb) << σ(pp) Events have to be selected with specific triggers Trigger requirements: large bandwidth, background suppression, deadtimeless 11/23/10 S. Behari, CDF Results, TIFR 20

21 Triggers for B Physics Single-/Di-lepton A high p T lepton or two leptons with lower p T J/Ψ modes, masses, lifetimes, x-section Yields higher than Run I (low Pt threshold, increased acceptance) lepton + displaced track - semileptonic sample p T (e/µ) > 4 GeV/c, 120 µm < d0(trk) < 1mm, p T (Trk) > 2 GeV/c Semileptonic decays, lifetimes, flavor tagging B Yields 3x Run I Two displaced vertex tracks - hadronic sample p T (Trk) >2 GeV/c, 120 µm < d0(trk) < 1mm, Σp T > 5.5 GeV/c X-section, branching ratios, B s mixing Primary vertex ~ 1 mm b decays Secondary vertex Impact parameter 11/23/10 S. Behari, CDF Results, TIFR 21

22 Interests in B Hadron Lifetimes I. Bigi et. al, Ann. Rev. Nucl. Part. Sci. 47 (1997) 591. B + Λ b Spectator model: b hadron lifetimes are equal. Pauli Interference: prolongs lifetimes, +5% for B +, +3% for Λ b Weak Annihilation and Exchange: reduce lifetimes -7% Λ b 11/23/10 S. Behari, CDF Results, TIFR 22

Interests in B Hadron Lifetimes Continued The B +,B 0 lifetimes are precisely measured at B-factories.

Odd trends of τ(λ b )/τ(b 0 ) ratios: WA Theory 1996: 0.78 ± 0.05 0.90-0.95 [LO + Spect.] 2004: 0.804 ± 0.

057 (CDF) Recent lifetime ratio world averages: PDG 2008 Theory O(1/m b 4 ) [2004] τ(b + )/τ(b 0 ) = 1.

23 Interests in B Hadron Lifetimes Continued The B +,B 0 lifetimes are precisely measured at B-factories. Experimental error on τ(b s0 )/τ(b 0 ) far higher than theory error! Odd trends of τ(λ b )/τ(b 0 ) ratios: WA Theory 1996: 0.78 ± [LO + Spect.] 2004: ± ± 0.05 [NLO+O(1/m b4 )] 2006: ± ± (CDF) Recent lifetime ratio world averages: PDG 2008 Theory O(1/m b 4 ) [2004] τ(b + )/τ(b 0 ) = ± 0.02 Gabbiani et al., PRD THEORY (NLO) τ(b s0 )/τ(b 0 ) = ± 0.01 τ(λ b )/τ(b 0 ) = ± 0.05 S. Behari, CDF Results, TIFR 11/23/10

24 Lifetime Measurements at CDF 11/23/10 S. Behari, CDF Results, TIFR 24

25 Lifetime Projections from the Fits B 0 :K s 0 B + Λ b 0 B 0 :K *0 11/23/10 S. Behari, CDF Results, TIFR 25

26 Fit Results τ B + τ B 0 τ Λ b 0 =1.639 ± 0.009(stat.) ± 0.009(syst.) ps =1.507 ± 0.010(stat.) ± 0.008(syst.) ps =1.537 ± 0.045(stat.) ± 0.014(syst.) ps (Weighted Avg) τ B + τ B 0 = ± 0.009(stat.) ± 0.004(syst.) τ Λ b 0 τ B 0 = ± 0.030(stat.) ± 0.008(syst.) (Theory: 0.86 ± 0.05) 11/23/10 S. Behari, CDF Results, TIFR 26

27 τ(b + ) Comparison 11/23/10 S. Behari, CDF Results, TIFR 27

28 τ(b 0 ) Comparison 11/23/10 S. Behari, CDF Results, TIFR 28

29 τ(λ b 0 ) Comparison Λ b Λ c π 11/23/10 S. Behari, CDF Results, TIFR 29

30 τ(b + )/τ(b 0 ) Comparison 11/23/10 S. Behari, CDF Results, TIFR 30

31 Observation of New Y(4140) State 11/23/10 S. Behari, CDF Results, TIFR 31

32 B+ yield: 115 ± 12 events Signal region: ± 3σ, Sidebands [-9,-6]σ or [6,9]σ Observation of Y(4140) Dalitz distribution shows events uniformly distributed in the expected phase space. Signal Sidebands 11/23/10 S. Behari, CDF Results, TIFR 32

33 Comparison of old and updated samples show clear enhancement in the signal region. ΔM unbinned likelihood fit: Signal: Rel. S-wave BW convoluted with a Gaus resolution function. Background: 3-body phase space Observation of Y(4140) B 0 s ψ φ contamination in high ΔM region modeled from MC. Yield: 19 ± 6 events, ΔM: MeV/c2 Width: MeV/c fb fb -1 11/23/10 S. Behari, CDF Results, TIFR 33

34 Significant excess above background at ΔM=1.18 GeV/c 2. Fitting it along with Y(4140) doesn t change the results compared to Y(4140)-only fit. Final results: Y(4140): Observation of Y(4140) m = (stat.) ± 0.6 (syst.) MeV/c 2 Γ = (stat.) ± 2.5 (syst.) MeV/c 2 Second peak: m = (stat.) MeV/c 2 Γ = (stat.) MeV/c 2 (Based on p-values from Toy MC tests) 11/23/10 S. Behari, CDF Results, TIFR 34

35 Summary The CDF Run II silicon detectors are in good health after 9 years of operation. Most ladders in SVX inner layers and the rest of the detector are expected be operable with high efficiency up to 12 fb -1, despite radiation damage to the sensors. L0 will begin to be affected beyond 12 fb -1, which does not affect CDF s vertex detection capability, nor b-vertex detection efficiency, significantly. World s best B s and Λ b lifetime measurements from CDF are in agreement with the world average and HQE predictions. The B + and B 0 lifetimes are competitive with B-factories. Observation of new hadrons and precision measurements of the properties of the established ones put the theoretical models to stringent tests. 11/23/10 S. Behari, CDF Results, TIFR 35

36 Backup Slides 11/23/10 S. Behari, CDF Results, TIFR 36

37 Detector Geometry L00 detail Beam pipe narrow sensors Cooling lines wide sensors carbon support 11/23/10 S. Behari, CDF Results, TIFR 37

38 Depleting a p-n Junction A p-n junction forms a region that is depleted of free charge carriers The depleted zone contains a non-zero fixed charge and an electric field. In this region electron hole pairs don t recombine but rather drift along field lines Dopant concentration Space charge density Carrier density Electric field p Depletion zone n Artificially increasing this depleted region by applying a reversed bias voltage allow charge collection from a larger volume Depletion voltage: V d = d 2 /(2ερµ) Electric potential p n h+e- 11/23/10 S. Behari, CDF Results, TIFR 38

39 Surface Damage Details Surface damage generation over time: Ionizing radiation creates electron/hole pairs in the SiO 2 Many recombine, electrons migrate quickly away Holes slowly migrate to Si/SiO 2 interface. Hole mobility is ~1/3 of that for electrons (450 cm 2 /V.s vs cm 2 /V.s) Some holes stick in the boundary layer Surface damage results in Increased interface trapped charge (see picture) Increase in fixed oxide charges Surface generation centers Electron accumulation under the oxide interface can alter the depletion voltage (depends on oxide quality and sensor geometry) In silicon strip sensors, surface damage effects (oxide charge) saturate at a few hundred krad Metal (Al) Oxide (SiO 2 ) Interface (SiO x ) Semiconductor (Si) After electron transport: After transport of the holes: /23/10 S. Behari, CDF Results, TIFR 39

40 Study of Signal to Noise Ratio The figure of merit of the sensors physics performance is the Signal to Noise Ratio (S/N) Signal: charge collected when a charged particle crosses the sensor Noise: intrinsic noise of the detector Signal Use J/ψ µ + µ - tracks Get total charge of cluster Decrease linearly with Lumi. Mean Strip Noise Average over strips in charge cluster Obtained from calibrations taken every two week. Square root increase with Lumi. 11/23/10 S. Behari, CDF Results, TIFR 40

B Hadron lifetimes using a displaced track trigger

B Hadron lifetimes using a displaced track trigger Why B Lifetimes are interesting Overview one analysis Results and prospects Sneha Malde University of Oxford 1 B Hadrons B Mesons B Baryons Name B + B