The CKM Matrix. If ν s have mass there will be analogous matrix. We need to connect the weak eigenstates of quarks with the mass eigenstates

Transcription

1 The CKM Matrix We need to connect the weak eigenstates of quarks with the mass eigenstates weak eigenstates V CKM mass eigenstates If ν s have mass there will be analogous matrix K. Honscheid, Ohio State University (1)

2 K. Honscheid, Ohio State University (2) Proper Formulation of CKM Matrix Good l 3 in real part & l 5 in imaginary part We know l=0.22, A~0.8; constraints on r & h Due unitarity there are 6 CKM triangles ( ) ( ) λ η ρ λ ηλ + λ λ η λ λ λ η ρ λ λ λ = 1 A i 1 A i 1 A A i i A V d s b u c t

3 The 6 CKM triangles ds - indicates rows or columns used There are 4 independent phases, which can be used to construct entire CKM matrix K. Honscheid, Ohio State University (3)

4 The 4 CKM Phases * V β = tbv arg * VcbV td cd γ = arg V V * ub * cb V V ud cd χ = arg V V * cs * ts V V cb tb χ = arg V V * ud * cd V V us cs β & γ probably large, χ small ~0.02, χ smaller K. Honscheid, Ohio State University (4)

5 Derive reference triangle K. Honscheid, Ohio State University (5)

6 Usual Triangle (for ref.) Real a, b & g must sum to 180 o Therefore, any two will do IF we are really measuring the intrinsic angles New physics can hide, only these angle measurements not sufficient. Ex: Suppose there is new physics in B o -B o mixing (q) & we measure CP in yk s and p + p -, then 2b =2b+q, 2a =2a-q, & 2b +2a =2b+2a, new physics but b +a +g= 180 o Two sides V ub /V cb & V td /V ts important. K. Honscheid, Ohio State University (6)

7 Ambiguities Suppose we measure sin(2b) using yk s, what does that tell us about b? Ans: 4 fold ambiguity- b, p/2-b, p+b, 3p/2-b Only reason h>0, is B k >0 from theory, and related theoretical interpretation of e K. Honscheid, Ohio State University (7)

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12 Heavy Quark Effective Theory HQET tells us that in first order when a b quark transforms to a c quark with the c going at the same velocity as the b, the form factor is 1 in first order AND the corrections to 1 can be calculated The form-factor therefore known to be 1- correction, at maximum q 2, called w=1, where ω = M + M 2M M 2 B B 2 D* D* q 2 K. Honscheid, Ohio State University (12)

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14 V cb from BfiD*l n Use BfiD*l n because the decay rate is largest for and the corrections are better determined. In HQET there is one universal form-factor function, so we don t have to deal with 3 formfactors To find V cb measure value at w=1, here D* is at rest in B rest frame * dγ(b D λν ) dω = 2 G F 48π 3 V cb 2 F 2 ( ω)(m B m D* 3 D* K. Honscheid, Ohio State University (14) ) 2 m ω 2 m 1 2ω mb 1 4ω( ω+ 1) m 1 m D* D* B + m m 2 2 D* 2 B

15 V cb results, an example To get results fit using shape proposed by Caprini et al, or Boyd & Grinstein, or in CLEO case by Stone Use F(1)=0.91±0.03, from Caprini, Uraltsev.. Results DELPHI: (41.2±1.5±1.8±1.4)x10-3 ALEPH: (34.4±1.6±2.3±1.4)x10-3 OPAL: (36.0±2.1±2.1±1.2)x10-3 CLEO: (39.4±2.1±2.2±1.3)x10-3 World Average ± by adding theoretical error in quadrature with exp error. K. Honscheid, Ohio State University (15)

16 Theoretical Value of F(1) Lim F(1) = 1 as m b fi, F(1)=1+O(a s /p)+d 1/m 2+d 1/m 3 (no d 1/m, Lukes thrm) F(1)=0.91±0.03, from Caprini, Uraltsev.. F(1)=0.89±0.06, from Bigi Can we get an accurate non-quenched value from the Lattice? The errors are not consistent. What do the errors mean? Bigi: In stating a theoretical error, I mean that the real value can lie almost anywhere in this range with basically equal probabilty rather than follow a Gaussian distribution. Furthermore, my message is that I would be quite surprised if the real value would fall outside this range. Maybe one could call that a 90% confidence level, but I do not see any way to be more quantitative. K. Honscheid, Ohio State University (16)

17 QCD Sum Rules for V cb Using Operator Product Expansion & Heavy Quark Expansion, in terms of a s (m b ), L, and the matrix elements l 1 and l 2, we can accurately determine V cb. These quantities arises from the differences λ1 + 3λ 2 λ1 λ2 mb mb = Λ + Κ, m * m B b = Λ + Κ 2m 2m b b From B*-B mass difference, l 2 = 0.12 GeV 2, Γ sl = G 2 F V cb 2 192π 3 m 5 B αs π Λ mb Λ 1.65 m λ 3.18 m B 1 2 B α π λ m 2 2 B s K. Honscheid, Ohio State University (17)

18 Measurement of G sl & moment analysis Use total Branching Ratio Measurement CLEO using lepton tags (10.49±0.17±0.43)% Lifetime 1.613±0.020ps Γ sl = 65.0±3.0 ns -1 (note LEP 68.6±1.6 ns -1 ) Moment Analysis of BfiXln, M x and E l K. Honscheid, Ohio State University (18)

19 Result for V cb Using Moment Analysis Discrepancy between hadronic mass moments and E l moments Theoretical estimates favor M x moments Taking M x estimates only: Λ = 0.33±0.02±0.08 GeV λ 1 =-0.13±0.01±0.06 GeV 2 Ligeti claims: V cb = , but it would be foolish to use it Is this an experimental problem or an inherent problem in OPE? K. Honscheid, Ohio State University (19)

20 A new measurement of V cb B 0 -> D *+ l - ν K. Honscheid, Ohio State University (20)

21 Results K. Honscheid, Ohio State University (21)

22 Is there a problem? K. Honscheid, Ohio State University (22)

23 Waiting for a V ub update Exclusive (B -> rln or pln) [CLEO] V ub = (3.25+/ /-0.55)x Inclusive (b -> X u ln) V ub / V cb = 0.8 +/- 0.2 Rare hadronic decays (e.g. B->pp) B->D (*) s p +(0) B -> tn [LEP, CLEO] (seen) (not seen) K. Honscheid, Ohio State University (23)

24 V ub from lepton endpoint BR & value of V ub depends on model, since fraction of leptons in signal region depends on model! Y(4S) data b cλν + continuum K. Honscheid, Ohio State University (24)

25 Neutrino Reconstruction K. Honscheid, Ohio State University (25)

26 V ub from pln and rln p + ln + p 0 ln r + ln + r 0 ln+ w o ln b u backrounds & cross-feeds b c backrounds b u backrounds & cross-feeds K. Honscheid, Ohio State University (26)

27 New CLEO form-factor Analysis Find ρ + λν + ρ 0 λν+ ω ο λν as function of E λ using likelihood method to fit M(ππ) & E distributions, where E = E ρ +E l + p miss -E beam E l >2.3 GeV/c ρ modes with E cut ρ modes with M(ππ) cut ρ modes with both cuts b ulν bkgrd b clν M(ππ) E E l K. Honscheid, Ohio State University (27)

28 Form-factor Results In general 3 form-factors for 0 - fi 1 - transitions, but we do not have enough precision to disentangle them Data shows the need for more data Combining with older result: V ub =( )x K. Honscheid, Ohio State University (28)

29 Summary of V ub Results LEP measurements use 8% theoretical error as given by Uraltsev. However Jin s similar calculation claims a 10% error but differs by 14%. I use a 14% theory error here Since the LEP Monte-Carlo calculations are highly correlated, I take a common 14% systematic uncertainty The exclusive channels rule out the Korner & Schuler (KS) model (gets the wrong V/P ratio), but have large errors The CLEO endpoint results have the best statistical error. Hard to estimate the theoretical error. I take 14%. K. Honscheid, Ohio State University (29)

30 Pure leptonic decays: B -> tn BR( B GF mbml m + l fi l + 2 n) = 1- fb V 2 2 ub 8p mb Ł ł t B b u W l ν Standard Model: B -> τν ~ (0.2-1) x 10-4 Idee: fully reconstruct on B, look for τ + missing energy Using 9.7 x 106 BB events we find BR(B -> τν ) < 8.4 x 10-4 Bonus: BR(B -> Kνν ) < 2.4 x 10-4 K. Honscheid, Ohio State University (30)

31 Strong Interaction if they get out fast enough... u u b c W u W creates ud pointlike color singlet d Hadronic But if... Strong Interaction u u d u b c W u d K. Honscheid, Ohio State University (31) u u Strong Interaction b c W n Semileptonic e Understanding Hadronic Decays

32 Hadronic B Decays Semileptonic Decay Hadronic + Factorization A = A = GF V 2 cb V GF V 2 * ub cb V < n g * ub < p m (1 - g 5 ) l >< ( du) 0 >< D D *- ( cb) B ( cb) B * - 0 > 0 > Factorization Tests: Branching Ratios Polarization dg 2 dq G( B fi D ( B fi D * + * + h - ln) ) q 2 = m 2 h = 6p 2 c 2 1 f 2 h V ud 2 G L /G (BfiD *+ h - ) = G L /G (BfiD *+ l - n ) q 2=m h 2 K. Honscheid, Ohio State University (32)

33 K. Honscheid, Ohio State University (33) (1997)

34 The D* + p + p - p - p o Final State (a) DE sidebands s (b) DE around 0 ±2.0s fit with sideband shape fixed & norm allowed to float Also signals in D o fik - p + p o and D o fik - p + p + p - (not shown) (D o K - π + ) 358±29 Fit B yield in bins of M(4p) K. Honscheid, Ohio State University (34)

35 The p + p - p o Mass Distribution What are the decay mechanisms for the (4p) - final state? We examine the p + p - p o mass spectrum (2 combinations/event). All 3 D o decay modes summed Enlarged & Dalitz plot exterior removed K. Honscheid, Ohio State University (35)

36 The wp - Mass Distribution Fit M B distribution in ωπ mass bins D + ωπ D ωπ Breit-Wigner: Mass = 1432±37 Γ = 376±47MeV All 3 D o decays used Breit-Wigner: Mass = 1367±75 Γ = 439±135MeV only D o K - π + Possible resonance (A) at M= MeV, G= MeV K. Honscheid, Ohio State University (36)

37 D *+ (wp) - Angular Distributions For a spin-0 A the D* & w would be fully polarized Spin 0 c 2 /dof = 3.5 (cosq D* ), 22 (cosq w ) Ruled out Best fit G L /G = (D *+ ), (w) Spin-0 expectation K. Honscheid, Ohio State University (37)

38 The Dwp - Final State D ωπ D + ωπ only D o K - π + only D+ K + π - π - 88±14 91±18 Signal: E <2σ (18MeV) Sideband: 3σ< E <7σ No signal in ω sidebands K. Honscheid, Ohio State University (38)

39 The wp - Mass Distribution Fit M B distribution in ωπ mass bins Breit-Wigner: Mass = 1415±43 Γ=419±110 MeV Combined D ωπ and D + ωπ modes (179 events) Consistent with D*ωπ result Select ( GeV) for angular study (104 events) K. Honscheid, Ohio State University (39)

40 The Angular Distributions in B fi D A - : A - fi w p -, wfi p p + p - between ω in A frame & A boost direction between normal of ω decay plane & ω boost between Α & ω decay planes Small efficiency corrections applied For 1 + and 2, the longitudinal ratio (Γ 1 - preferred, χ 2 /dof (1 - ) = 1.7, (2 + L /Γ) floats ) = 3.2 A - properties: mass = 1418±26±19 MeV, Γ=388±41±32 MeV K. Honscheid, Ohio State University (40)

41 Identifying the A - with the r Clegg & Donnachie: (tfi(4p)n, e + e - fip + p -, p + p + p - p - ) find two 1 - states with (M, G)= ( , ) MeV & ( , ) MeV, mixed with non-qq states, only the lighter one decays to wp Godfrey & Isgur: Predict first radial excited r at 1450 MeV, G=320 MeV, B (r - fiwp - )=39% K. Honscheid, Ohio State University (41)

42 Summary & Discussion of Rates Mode Br (%) # of events B D + π π + π π 1.72±0.14± ±70 B D + ωπ 0.29±0.03± ±15 B D + ωπ 0.28±0.05± ±18 B D π π + π π 1.80±0.24± ±26 B D ωπ 0.45±0.10± ± 6 B D ωπ 0.41±0.07± ±14 r dominates the wp - final state G(B fid *+ r - ) / G(B fid + r - ) = G(B - fid * r - ) / G(B - fid r - ) = G(BfiD * r - ) / G(BfiDr - ) = Consistent with Heavy Quark Symmetry prediction ( ratio = 1 ) With B (r - fiwp - )=39%, G(BfiD (*) r - ) ~ G(BfiD (*) r - ) K. Honscheid, Ohio State University (42)

43 Testing Factorization Polarization: Γ L /Γ (B D + h ) = Γ L /Γ (B D + l ν ) q 2=m h 2 Branching Fractions: Γ(B D + h ) / dγ/dq 2 (B D + l ν ) q2=mh 2 = 6π 2 c 12 f h2 V ud 2 Using B (ρ ωπ )=39% f ρ = 167 ± 23MeV K. Honscheid, Ohio State University (43)

44 Extending q 2 : B fi D*D s * Final State D * + D - s D * + D - s D (* )+ D s ** o B(%) D* + + r - r - D S - G L /G (%) K. Honscheid, Ohio State University (44)

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46 Color Suppression in B Decays... CLEO: No Signal! works K. Honscheid, Ohio State University (46)

47 Charged B Decay and Interference B 0 Decay u b W W b c d d d d Decay B 0 ->D - p + B 0 ->D 0 p 0 B + ->D 0 p + Different final states Interference c u d d W b u u b c d W u u c u d u BSW: a 1 a 2 a 1 + z a 2 a 1, a 2 are phenomenological constants process dependent great success in charm decay: destructive interference smaller G Hadronic for D + t D+ >> t D0 Mode B 0 (x10-3 ) B + (x10-3 ) Dπ 3.0+/ /-0.5 Dρ 7.9+/ /1.8 Da /-3.3 Dρ 2.8+/ /-0.8 D*π 2.8+/ /-0.4 D*ρ 6.8+/ /-3.1 D*a 1 13+/ /-5 D*ρ 2.9+/ /-0.8 K. Honscheid, Ohio State University (47)

48 More on charged B Decays K. Honscheid, Ohio State University (48)

49 Rare B Decay Tree: u Penguin: u s u u u K π 0 s π d u K s d u u u π 0 π Tree decays bfiu vs. bfic suppressed by V ub 2 / V cb 2 ~ 0.01 Additional V us 2 / V ud 2 ~ 0.04 for K - Expect tree dominantly bfiuud. Decays bfis,d GIM-suppressed Loop diagram (m t /m W ) 2. V td 2 / V ts 2 ~ 0.01 Expect penguins dominantly bfiuus. K. Honscheid, Ohio State University (49)

50 B fi K + p - /p + p - Topology B fi Kp e + e -- fi qq P daughter ~ GeV/c (higher than for b c decays) Major background from e + e - qq continuum Continuum events are jetty in topology P B ~ 300 MeV/c BB events spherical Continuum suppression from ML fit to several kinematic and topological variables (more efficient). Continuum suppression factor of ~ 10 6, efficiency for Kπ/ππ of ~ 40% K. Honscheid, Ohio State University (50)

51 K/p Separation Kp vs. pp from de/dx in drift chamber Resol. confirmed with D * D 0 π, D 0 K π + Also separation from kinematics: Pions Kaons DE pp = E p + E p - E beam Kπ ππ CLEO data E resolution studied with D 0 K π + (π 0 ) mass resolutions s DE DE (de/dx - Expected)/σ de/dx CLEO II 25 MeV 1.7s 1.7s E ππ (GeV) CLEO II.V 20 MeV 2.1s 2.0s K. Honscheid, Ohio State University (51)

52 Fit Results for B Kπ, B ππ K. Honscheid, Ohio State University (52)

53 BfiKp, Bfipp Summary Signal (events) # s e (%) BR ( 10-6 ) p + p - p + p 0 p 0 p < 12.7 < 5.7 K + p - K + p 0 K 0 p + K 0 p 0 K + K - K + K < 1.9 < 5.1 K. Honscheid, Ohio State University (53)

54 Comparision of B-> pp Results K. Honscheid, Ohio State University (54)

55 Problems with measuring a using B o fip + p - Using B o fip + p - would be nice, but large Penguin term, CLEO: B(B o fip + p - ) ~ 0.8 x 10-5, while B(B o fik + p - ) =(1.4±0.3±0.2)x10-5 The effect of the Penguin must be measured in order to determine a. Can be done using Isopsin, but requires a rate measurements of p - p o and p o p o (Gronau & London). However, this is daunting. for s get K - K. Honscheid, Ohio State University (55)

56 Measuring a using B o firp fi p + p - p o A Dalitz Plot analysis gives both sin(2a) and cos(2a) ( Snyder & Quinn) CLEO has measured the branching ratios B(B - fir o p -) = (1.5±0.5±0.2)x B (B o fir - p + + r + p - ) =(3.5±1.0±0.5)x10-5 Snyder & Quinn showed that tagged events are sufficient K. Honscheid, Ohio State University (56)

57 Comparison of rp modes Final State: r - p + r + p - r - p o r o p - r o p o CLEO(10-5 ): <3.5±1.2> < ±0.5±0.2 <1.8 Ciuchini et al.: Ali et al.: B(B + fi r o K + ) = < 90% c.l. (CLEO) {To measure the three neutral rp modes, requires triggering on hadronic decays with high efficiency, RICH particle ID and high quality photon detection} K. Honscheid, Ohio State University (57)

58 Ways of measuring g May be easier to measure than a There are 4 ways of determining g Time dependent flavor tagged analysis of B s D s K Measure rate difference between B - D o K - and B + D o K + Rate measurements in K o π ± and K ± π µ (Fleisher-Mannel)or rates in K o π ± & asymmetry in K ± π ο (Neubert-Rosner). Has theoretical uncertainties but can be useful. Use U spin symmetry d s: measure time dependent asymmetries in both B o π + π & B s K + K (Fleischer). Ambiguities here as well but they are different in each method, and using several methods can resolve them. K. Honscheid, Ohio State University (58)

59 ± B s fid s K m Decay processes Diagrams for the two decay modes, B ~ 10-4 for each K. Honscheid, Ohio State University (59)

60 B - fi[k + p - ]K - Decay processes B ~ 10-6 B ~ 2x10-7 K. Honscheid, Ohio State University (60)

61 Exclusive b fi u Transitions Many hadronic b fi u transitions observed New study includes 14 channels (hep-ex/ ) In general - good agreement with theory Full Dalitz analyses could determine a and g K. Honscheid, Ohio State University (61)

62 Likelihood Contours Bfir + p/rk and Bfir 0 p/rk fitted simulataneously BR(Bfir + p)/br(bfir 0 p) smaller than expected (>4) K. Honscheid, Ohio State University (62)

63 Modes with h and h K. Honscheid, Ohio State University (63)

64 Pure Penguins: B fi fk K. Honscheid, Ohio State University (64)

65 arg(v ub ) (= g ) from Decay Rates Fleischer-Mannel (Phys. Rev. D57, 2752(1998)) Γ(B 0 K π + ) Γ(B + K 0 π + ) R sin 2 γ CLEO: R = 1.01 ± 0.26 Neubert-Rosner (Phys. Lett. B441, 403 (1998)) R * Γ(B + K 0 π + ) 2Γ(B + K + π 0 ) (1-R * )/ε 3/2 δ EW - cosγ 0.58 ± 0.74 (0.64 ± 0.15) - cosγ Also model-dependent fit to many CLEO branching ratios of pp, Kp, rp, wp (Wuerthwein et al. hepex/ ): 84 < g < 154 (90% C.L.) K. Honscheid, Ohio State University (65)

66 Search for Direct CP Violation K. Honscheid, Ohio State University (66)

67 Search for Direct CP Violation K. Honscheid, Ohio State University (67)

68 CP Asymmetries Measure B and B reactions described by two amplitudes: Γ(B f) = a 1 e i(φ 1+δ1) + a 2 e i(φ 2+δ2) 2 Γ(B f) = a 1 e i( φ 1+δ1) + a 2 e i( φ 2+δ2) 2 CP asymmetry from strong and weak phase differences (Γ Γ) / (Γ + Γ) sin(φ 1 φ 2 )sin(δ 1 δ 2 ) Depends upon comparable magnitudes as well CLEO can measure decays that are sensitive to g = arg(v ub *) B + K + π 0, B + K 0 π +, B + K + η K. Honscheid, Ohio State University (68)

69 A cp Expectations Factorization model calculations (no FSI interactions) Ali, Kramer, Liu, hep-ph/ » K + π » K + π » K 0 π » K + η » ωπ Final state interactions may boost A CP ~ 20-40%. He et al, Phys. Rev. Lett. 81, 5738 (1998) Neubert, JHEP 9902, 014 (1999) Deshpande et al., Phys. Rev. Lett. 82, 2240 (1999) New physics could boost A CP ~ 40-60%. He et al., hep-ph/ K. Honscheid, Ohio State University (69)

70 Experimental Bias(es) B flavor tagged by high momentum track Must demonstrate reconstruction not charge dependent. Charge difference in K - N and K + N cross sections Track reconstruction difference confirmed in Monte Carlo ~ K. Honscheid, Ohio State University (70)

71 CP Asymmetry Results events events events events events K - p + K + p 0 K 0 p + K + h wp + 90% C.L. K. Honscheid, Ohio State University (71) A CP

72 CP from New Physics? 126 ± 15 events Penguin amplitude V ts Other amplitudes, CP, small in SM Some Higgs models introduce CP, possibly even if bfisg rate unaffected. Wolfenstein & Wu, Phys. Rev. Lett. 73, 2809 (1998) Asatrian & Ioannissian, Phys. Rev. D54, 5642 Kagan & Neubert, Phys. Rev. D58, B Candidate Mass (GeV/c 2 ) K. Honscheid, Ohio State University (72)

73 bfisg Results Updated branching ratio results: Monte Carlo BR(B 0 fik *0 g) = ( ) 10-5 BR(B + fik *+ g) = ( ) 10-5 BR(BfiK 2 * (1430)g) = ( ) 10-5 CP asymmetry from special kinematic region for best K/p identificatio A CP = Asymmetry for inclusive bfisg (based on 9.7M BB pairs only): A CP = or < A CP < 0.09 (90% C.L.) Upper limit on b d exclusive penguins: BR(B (ρ,ω )γ) < ~10-5 K. Honscheid, Ohio State University (73)

74 Search for bfidg Expect that Bfirg also described by penguin amplitude - dominant top? G(B firg) V td 2 G(BfiK * g) V ts 2 = ξ ξ Updated branching ratio limits: BR(B 0 fir 0 g) < BR(B + fir + g) < BR(B 0 fiwg) < BR(Bfirg)/BR(BfiK*g )<0.32 (90%CL) K * g rg V td /V ts < 0.72 (90%CL) K. Honscheid, Ohio State University (74)

75 Short Term Future B Factories (BABAR, Belle, (CLEO)) sin(2β) with ~5-10% precision Rare decays with BR ~10-6 Better understanding of V cb and V ub Hadron colliders HERA-b has the potential to also measure sin(2β) CDF already has already taken the first steps toward measuring sin(2β). Next run will start ~Aug CDF could also measure x s. K. Honscheid, Ohio State University (75)

76 Why do b & c decay physics at hadron colliders? Large samples of b quarks are available, with the Fermilab Main Injector, the collider will produce ~4x10 11 b hadrons per 10 7 sec at L = 2x10 32 cm - 2 s -1. e + e - machines operating at the Y(4S) at L of 3x10 33 produce 6x10 7 B s per 10 7 s. B s & L b and other b-flavored hadrons are accessible for study. Charm rates are ~10x larger than the b rate K. Honscheid, Ohio State University (76)

77 Main detector challenges Problems: σ b /σ tot ~ 1/500 at Fermilab, 1/100 at LHC Background from b s can overwhelm rare processes Large data rate just from b s - 1 khz into detector Large rates cause Radiation damage to EM calorimeter; photon multiplicities may obscure signals Solutions for BTeV: Use detached vertices for trigger and background rejection Have excellent charged particle identification & lepton id Dead-timeless trigger and DAQ system capable of writing khz of events to tape Use PbWO 4 crystal calorimeter K. Honscheid, Ohio State University (77)

78 Fundamental Detector Principles Necessary to trigger efficiently on purely hadronic final states - detached vertex trigger Necessary to reconstruct final states with excellent decay time resolution, good efficiency and mass resolution Necessary to detect final states with g or p o efficiently with good energy resolution Necessary to able to identify p/k/p K. Honscheid, Ohio State University (78)

79 The BTeV Detector Inside the beam pipe -PbWO 4 crystals K. Honscheid, Ohio State University (79)

80 The C0 Interaction Region Construction finished BTeV is designed to be compatible K. Honscheid, Ohio State University (80)

81 The LHCb Detector K. Honscheid, Ohio State University (81)

82 The BTeV Pixel Detector Pixels necessary to eliminate ambiguity problems with high track density; Essential to our detached vertex trigger Crucial for accurate decay length measurement Radiation hard Low noise K. Honscheid, Ohio State University (82)

83 Pixel Trigger Description Triplets used to get space point & mini-vector, called a station hit Station hits are organized into f-slices Tracks are found in these f-slices full pattern recognition is performed Minimum track p cuts are applied Event level processors then find primary vertices & detached tracks K. Honscheid, Ohio State University (83)

84 Detached Vertex Trigger Level I Trigger uses information from the Pixel Detector to find the primary vertex and then look for tracks that are detached from it The simulation does the pattern recognition. It uses hits from MCFast including multiple scattering, bremsstrahlung, pair conversions, hadronic interactions and decays in flight Detailed studies of efficiency and rejection for up to an average of three interactions/crossing K. Honscheid, Ohio State University (84)

85 BTeV Trigger Performance For a requirement of at least 2 tracks detached by more than 4s, BTeV triggers on only 1% of the beam crossings and achieve the following efficiencies for these states: State efficiency(%) State efficiency(%) B π + π - 55 B o K + π - 54 B s D s K 70 B o J/ψ K s 50 B - D o K - 60 B s J/ψK * 69 B - K s π - 40 B o K * γ 40 K. Honscheid, Ohio State University (85)

86 B o fip + p - : L/s distribution L/s = Decay length/error is very important in rejecting background both at trigger level and in analysis Much better in Forward (BTeV) geometry than Central geometry because b s are moving faster L/σ K. Honscheid, Ohio State University (86)

87 A sample calculation: B o fip + p - BTeV LHCb Cross-section 100 µb 500 µb Luminosity 2x x10 32 # of B o /Year (10 7 s) 1.4x x10 11 B(B o π + π - ) 0.75x x10-5 Reconstruction efficiency Triggering efficiency (after all other cuts) # (π + π - ) 34,000 28,560 εd 2 for flavor tags (K ±, λ ±, same + opposite side jet tags) # of tagged π + π - 3,400 2,900 Signal/Background Error in π + π - asymmetry (including bkgrd) ±0.023 ±0.019 K. Honscheid, Ohio State University (87)

88 Comparisons of BTeV With e + e - B factories Number of flavor tagged B o fip + p - (B=0.75x10-5 ) L (cm -2 s -1 ) σ #B o /10 7 s ε εd 2 #tagged e + e - 3x nb 3.0x BTeV 2x µb 1.4x Number of B - fid o K L(cm -2 s -1 ) σ #B o /10 7 s ε # e + e - 3x nb 3.0x BTeV 2x µb 1.4x B s, B c and L b not done at Y(4S) e + e - machines Number of tagged, reconstructed B o decays to rp is a factor of at least 10 higher for BTeV. K. Honscheid, Ohio State University (88)

89 Comparisons of BTeV with LHCb Advantages of LHCb σ b 5x larger at LHC, while σ t is only 1.6x larger The mean number of interactions per beam crossing is 3x lower at LHC, when the FNAL bunch spacing is 132 ns LHCb HAS BEEN APPROVED! Advantages of BTeV (machine specific) The 25 ns bunch spacing at LHC makes 1st level detached vertex triggering more difficult. The 7x larger LHC beam energy causes problems: much larger range of track momenta that need to be analyzed and large increase in track multiplicity, which causes triggering and tracking problems The long interaction region at FNAL, σ=30 cm compared with 5 cm at LHC, somewhat compensates for the larger number of interactions per crossing, since the interactions are well separated K. Honscheid, Ohio State University (89)

90 Comparisons with LHCb II Advantages of BTeV (detector specific) BTeV is a two-arm spectrometer (gives 2x advantage) BTeV has vertex detector in magnetic field which allows rejection of high multiple scattering (low p) tracks in the trigger BTeV is designed around a pixel vertex detector which has much less occupancy, and allows for a detached vertex trigger in the first trigger level. Important for accumulation of large samples of rare hadronic decays and charm physics. Allows BTeV to run with multiple interactions per crossing, L in excess of 2x10 32 cm -2 s -1 BTeV will have a much better EM calorimeter K. Honscheid, Ohio State University (90)

91 K. Honscheid, Ohio State University (91)

92 K. Honscheid, Ohio State University (92)