richman

50 %
50 %
Information about richman
Entertainment

Published on October 15, 2007

Author: Natalia

Source: authorstream.com

B Physics and CP Violation:  B Physics and CP Violation Jeffrey D. Richman UC Santa Barbara CTEQ Summer School Madison, June 7-8, 2002 Outline (Lecture 1):  Outline (Lecture 1) Overview of B decays Why B physics is interesting; overview of decay diagrams; introductory discussion of CP violation. Accelerators and b-quark production The BaBar Detector Identifying B decays B-meson lifetimes and mixing CP Violation (CPv) and the CKM matrix the CKM hierarchy and the prediction of large CP asymmetries in B decays Outline (Lecture 2):  Outline (Lecture 2) CP Asymmetries: sin(2b): the golden measurement the struggle for the other angles Rare decays Penguins are everywhere! Semileptonic decays, decay dynamics, and the magnitudes of CKM elements. Heavy-quark symmetry and Vcb Prospects and future directions A reference: J. Richman, Les Houches lectures, 1997. http://hep.ucsb.edu/papers/driver_houches12.ps (or send e-mail asking for a copy: richman@charm.physics.ucsb.edu) Remarks/disclaimers:  I will be unashamedly pedagogical, and I will not aim for the level of impartiality that is customary in a review talk or article. I will be unashamedly selective: many important topics have been left out. There will be a strong bias towards recent results from e+e- colliders at the Y(4S). This is probably not too misleading for now, since BaBar, Belle, and CLEO have to some extent defined the state of the art, especially in CPv and rare decays. However, soon-to-come measurements from the Fermilab Tevatron (CDF, D0) will be of major importance. My own background in b physics: BaBar, CLEO I strongly encourage you to ask questions! Remarks/disclaimers Goals of B (and Bs) Physics :  Goals of B (and Bs) Physics Can CP violation be understood quantitatively within the Standard Model, or is new physics needed? Perform a comprehensive set of measurements to check for the presence non-SM CP-violating phases. Make precise measurements of the Standard Model CKM parameters: |Vcb |, | Vub |, |Vtd |, |Vts |, a, b, g,... Map out and understand rare B decays, especially processes with loops that can be very sensitive to particles outside the Standard Model. Understand the dynamics of B decays: underlying weak interaction process with overlay of complex strong interaction effects. Progress: HQET, lattice QCD, many measurements to test predictions. Overview of B Decays :  Overview of B Decays b is the heaviest quark that forms bound states with other quarks (t-quark decays too rapidly). m(b)<m(t) => the b-quark is forced to decay outside of its own generation Dominant decays are CKM suppressed: Relatively long B lifetime: Silicon tracking systems have been essential tools. Largest single branching fraction: Many interesting rare decay processes are experimentally accessible (b->uW, gluonic penguins, electroweak penguins). Leptonic and Semileptonic Decays:  Leptonic and Semileptonic Decays Leptonic B+ decay not yet observed! Largest expected mode is: Ignoring photon radiation: Used to measure magnitudes of CKM elements: Vcb and Vub Amplitude can be rigorously parametrized in terms of form factors. Hadronic Decays: Tree Diagrams:  Hadronic Decays: Tree Diagrams Theoretical predictions very difficult. Naïve factorization model works reasonably well in predicting pattern of decays. “Color suppressed” Naïve factorization model probably breaks down. (New data on B->D0p0 and B->D*0p0.) The color allowed and color suppressed amplitudes interfere constructively in charged B decays. (Opp. effect for D+.) Processes with loops: sensitivity to new particles:  Processes with loops: sensitivity to new particles Both gluonic and electoweak penguins have been observed! The SM mixing rate is dominated by tt (off-shell) intermediate states. Processes used for sin2b measurement :  Processes used for sin2b measurement A color suppressed decay! However, in this case, the rate is enhanced by the relatively large decay constant of the J/y: Decay modes for sin2b measurement:  Decay modes for sin2b measurement The C, P, and T Transformations:  The C, P, and T Transformations C, P, and T are discrete transformations: there is no continuously varying parameter, and these operations cannot be constructed from successive infinitesimal transformations. In all well-behaved quantum field theories, CPT is conserved. A particle and its antiparticle must have equal mass and mean lifetime. P and C violation in Weak Interactions is Maximal (V-A):  P and C violation in Weak Interactions is Maximal (V-A) P C Allowed Allowed Not Allowed A First Look at CP violation :  A First Look at CP violation The discovery of CP violation in 1964 was based on the demonstration that the mass eigenstate KL is not an eigenstate of CP, so . The lifetime separation between BH and BL is tiny, so we must use a different method, in which we compare the rates for CP-conjugate processes. Remove Ks from beam using lifetime difference. CPv small in kaon system! The Legacy of Kaon Physics:  “...the effect is telling us that at some tiny level there is a fundamental asymmetry between matter and antimatter, and it is telling us that at some tiny level interactions will show an asymmetry under the reversal of time. We know that improvements in detector technology and quality of accelerators will permit even more sensitive experiments in coming decades. We are hopeful then, that at some epoch, perhaps distant, this cryptic message from nature will be deciphered.” ...J.W. Cronin, Nobel Prize lecture*. J.W. Cronin and V.L. Fitch, Nobel Prize 1980. *J.W. Cronin, Rev. Mod. Phys. 53, 373 (1981). J.H. Christenson, J.W. Cronin, V.L. Fitch, and R. Turlay, Phys. Rev. Lett. 13, 138 (1964). The Legacy of Kaon Physics CP violation and alien civilizations:  CP violation and alien civilizations We can use our knowledge of CP violation to determine whether alien civilizations are made of matter or antimatter, without having to touch them. Long-lived neutral kaon We have these inside of us CP Violation and Cosmology:  CP Violation and Cosmology A. Sakharov noted (1967) that CP violation has an important connection to cosmology. 3 conditions for an asymmetry between N(baryons) and N(anti-baryons) in the universe (assuming equal numbers initially due to thermal equilibrium). baryon-number-violating process both C and CP violation (helicities not relevant to particle populations) departure from thermal equilibrium How can CP asymmetries arise? (I):  How can CP asymmetries arise? (I) When we talk about CP violation, we need to talk about the phases of QM amplitudes. This is usually very confusing. some phases are physical; others are not. many treatments invoke specific phase conventions, which acquire a magical aura. Need to consider two types of phases CP-conserving phases: don’t change sign under CP. (Sometimes called strong phases since they can arise from strong, final-state interactions.) CP-violating phases: these do change sign under CP. How can CP asymmetries arise? (II):  How can CP asymmetries arise? (II) Suppose a decay can occur through two different processes, with amplitudes A1 and A2. First, consider the case in which there is a (relative) CP-violating phase between A1 and A2 only. No CP asymmetry! (Decay rate is different from what is would be without the phase.) How can CP asymmetries arise? (III):  How can CP asymmetries arise? (III) Next, introduce a CP-conserving phase in addition to the CP-violating phase. Now have a CP asymmetry Measuring a CP-violating phase:  Measuring a CP-violating phase To extract the CP-violating phase from an observed CP asymmetry, we need to know the value of the CP-conserving phase. In direct CP-violating processes we usually do not know the relative CP-conserving phase because it is produced by strong-interaction dynamics that we do not understand. B production at the Y(4S):  B production at the Y(4S) Rate of events vs. total energy in e+e- CM frame: TM No accompanying pions! The B-meson energy is known from the beam energy. (CLEO, CLNS 02/1775) The New e+e- B factories:  The New e+e- B factories The machines have unequal (“asymmetric”) energy e+ and e- beams, so two separate storage rings are required. PEP-II: E(e-)=8.992 GeV E(e+)=3.120 GeV bg=0.55 The machines must bring the beams from the separate rings into collision. KEK-B: +-11 mrad crossing angle PEP-II: magnetic separation With two separate rings, the machines can store huge numbers of beam bunches without parasitic collisions. KEK-B: 1224 bunches/beam; I(e+)=716 mA; I(e-)=895 mA PEP-II: 831 bunches/beam; I(e+)=418 mA; I(e-)=688 mA CESR (single ring): 36 bunches/beam; I(e+)=I(e-)=365 mA PEP-II e+e- Ring and BaBar Detector:  PEP-II e+e- Ring and BaBar Detector Linac PEP-II ring: C=2.2 km BaBar LER (e+, 3.1 GeV) HER (e-, 9.0 GeV) BaBar May 26, 1999: 1st events recorded by BaBar The Y(4S) Boost:  The Y(4S) Boost The purpose of asymmetric beam energies is to boost the B0B0 system relative to the lab frame. By measuring Dz, we can follow time-dependent effects in B decays. The distance scale is much smaller than in the kaon decay experiments that first discovered CP violation! From CESR (1 ring, E symmetric) to PEP-II (2 rings, E asymmetric):  From CESR (1 ring, E symmetric) to PEP-II (2 rings, E asymmetric) Pretzel orbits in CESR (36 bunches, 20 mm excursions) Top view of PEP-II interaction region showing beam trajectories. (10X expansion of vertical scale) The race between BaBar/PEP-II and Belle/KEK-B:  The race between BaBar/PEP-II and Belle/KEK-B Belle Exceeds design luminosity! e+e- vs. pp and pp:  e+e- vs. pp and pp Production cross sections Y(4S): pp at Tevatron: pp at LHC: b fraction (ratio of b cross section to total hadronic cross section) Y(4S): 0.25 pp at Tevatron: 0.002 pp at LHC: 0.0063 Comments Triggering: so far, most B branching fractions have been measured at e+e- machines, because CDF, D0 triggers were very selective in Run 1. Also, PID & g detection are better at Y(4S) experiments so far.) Hadron colliders produce Bs and b-baryons. (LEP also.) New displaced-vertex triggers at hadron-collider experiments should make a dramatic improvement. The BABAR Detector:  The BABAR Detector DIRC (particle ID) 1.5 T solenoid CsI (Tl) Electromagnetic Calorimeter Drift Chamber Instrumented Flux Return Silicon Vertex Tracker e+ (3.1GeV) e- (9 GeV) SVT: 97% efficiency, 15mm z resol. (inner layers, perpendicular tracks) Tracking : s(pT)/pT = 0.13% PT  0.45% DIRC : K-p separation >3.4s for P<3.5GeV/c EMC: E/E = 1.33% E-1/4  2.1% BaBar Detector :  BaBar Detector e- e+ center line CsI crystals Drift chamber Superconducting magnet (1.5 T) Muon detector & B-flux return Silicon Vertex Tracker DIRC: quartz bars standoff box PM tubes BaBar Event Display (view normal to beams):  BaBar Event Display (view normal to beams) Rdrift chamber=80.9 cm (40 measurement points, each with 100-200 mm res. on charged tracks) EM Calorimeter: 6580 CsI(Tl) crystals (5% g energy res.) Silicon Vertex Tracker 5 layers: 15-30 mm res. Cerenkov ring imaging detectors: 144 quartz bars (measure velocity) Tracking volume: B=1.5 T Innermost Detector Subsystem: Silicon Vertex Tracker:  Innermost Detector Subsystem: Silicon Vertex Tracker Be beam pipe: R=2.79 cm Installed SVT Modules (B mesons move 0.25 mm along beam direction.) BaBar Silicon Vertex Tracker:  BaBar Silicon Vertex Tracker 5 layers of double-sided silicon-strip detectors (340) 80 e-/hole pairs/mm Slide34:  Measure angle of Cherenkov cone Transmitted by internal reflection Detected by PMTs Particle Identification (DIRC) (Detector of Internally Reflected Cherenkov Light) No. light bounces (typical)=300 Slide35:  DIRC c resolution and K- separation measured in data  D*+ D0+  (K-+)+ decays Particle Identification with the DIRC. s(qc)  2.2 mrad >9s 2.5s K/p Separation Particle Identification:  Particle Identification Electrons – p* > 0.5 GeV shower shapes in EMC E/p match Muons – p* > 1 GeV Penetration in iron of IFR Kaons dE/dx in SVT, DCH C in DRC E/p from E.M.Calorimeter Shower Shape e e p p 1 < p < 2 GeV/c 0.8 < p < 1.2 GeV/c E/p > 0.5 e p e p qc from Cerenkov Detector e p 0.5 < p < 0.55 GeV/c dE/dx from Dch 0.8 < p < 1.2 GeV/c Identifying B Decays in BaBar:  mes DE mes  3 MeV s DE  15 MeV All Ks CP modes Nsig  750 Purity 95% Identifying B Decays in BaBar Select “candidate daughter particles” using particle ID, etc. Compute the total 4-momentum: (E, p)=(E1+E2+E3, p1+ p2 +p3) Compute invariant mass: m2=E2-|p|2 Gives 10x improvement in mass resolution. sin2b Signal and Control Samples:  sin2b Signal and Control Samples J/Y Ks (Ks  p+p-) J/Y Ks (Ks  p0p0) J/Y K*0 (K*0  Ksp0) c1 Ks Y(2s) Ks J/Y KL Bflav mixing sample J/Y Ks (Ks  p0p0) J/Y Ks (Ks  p+p-) J/Y K*0 (K*0  Ksp0) CP=-1 CP=+1 The Lorentz Boost:  The Lorentz Boost The asymmetric beam energies of PEP-II allow us to measure quantities that depend on decay time. e- 9.0 GeV e+ 3.1 GeV Measurement of Decay Time Distributions:  Measurement of Decay Time Distributions B0 decay time distribution background (linear scale) Slide41:  B0 and anti-B0 mesons spontaneously oscillate into one another! (Mixing also occurs with neutral kaons.) Neutral B mesons can be regarded as a coupled, two-state system. To find the mass eigenstates we must find the linear combinations of these states that diagonalize the effective Hamiltonian. Interpretation of the Effective Hamiltonian:  Interpretation of the Effective Hamiltonian The effective Hamiltonian for the two-state system is not Hermitian since the mesons decay. Quark masses, strong, and EM interactions Decays CP Violation in Mixing:  CP Violation in Mixing Compare mixing for particle and antiparticle off-shell off-shell on-shell on-shell CP-conserving phase CP violation in mixing, continued:  CP violation in mixing, continued To produce a CP asymmetry in mixing, M12 and G12 must not be collinear and both must be nonzero: No CP violation in mixing CP violation in mixing Time evolution of states that are initially flavor eigenstates:  Time evolution of states that are initially flavor eigenstates General case; allows CP violation. CP Violation in B Mixing is Small:  CP Violation in B Mixing is Small When CP violation in mixing is absent (or very small), we have In the neutral B-meson system, the states that both B0 and B0 can decay into have small branching fractions, since normally lead to different final states. Can have (Cabibbo suppressed) and (b->u is CKM suppressed). So the SM predicts not yet observed Time evolution of states that are initially flavor eigenstates:  Time evolution of states that are initially flavor eigenstates In these formulas, we have assumed that DG/G<<1 and have set The Oscillation Frequency (Dm):  The Oscillation Frequency (Dm) In the neutral B-meson system, the mixing amplitude is completely dominated by off-shell intermediate states (Dm) [contrast with the neutral kaon system]. Calculation of the mixing frequency Time-dependent mixing probabilities and asymmetry Slide49:  Tagging CP asymmetry is between B0  fcp and B0  fcp Must tag flavor at Dt=0 (when flavor of two Bs is opposite). Use decay products of other (tag) B. Leptons : Cleanest tag. Correct 91% Kaons : Second best. Correct 82% b W- c s u d K- W+ b W+ c s u d K+ W- Effect of Mistagging and Dt Resolution:  Effect of Mistagging and Dt Resolution No mistagging and perfect Dt Nomix Mix Dt Dt D=1-2w=0.5 D=1-2w=0.5 Dt res: 99% at 1 ps; 1% at 8 ps w=Prob. for wrong tag Dt Dt Slide51:  NoMix(t)-Mix(t) NoMix(t)+Mix(t) T=2p/Dm ~D Dm = (0.516  0.016  0.010) ps-1 Measure mixing on control sample: constrain model of Dt resolution measure dilution D = (1-2w) CP violation in the Standard Model:  CP violation in the Standard Model In the SM, the couplings of quarks to the W are universal up to factors that are elements of a unitary, 3x3 rotation matrix Vij of the quark fields. This matrix originates in the Higgs sector (mass generation of quarks). W- e- ne b u W- W+ The Standard Model “Unitarity Triangle”:  The Standard Model “Unitarity Triangle” Weak interaction eigenstates Quark mass eigenstates Cabibbo-Kobayashi-Maskawa (CKM) matrix [Col 1][Col 3]*=0 V has only 4 real parameters, including 1 CP-violating phase. If just 2 quark generations: no CP phase allowed! CPv 1 of 6 equal-area triangles: orientation is just an unphysical phase The Structure of the CKM Matrix:  The Structure of the CKM Matrix The CKM matrix exhibits a simple, hierarchical structure (which we do not understand) with 4 real parameters. 0.04 (All unitarity triangles have same area, corresponding to the sizes of interference terms between 1st order weak amps. But we care about CP asymmetries, so the angles of the triangles also matter.) End of Lecture 1:  End of Lecture 1 Outline (Lecture 2):  Outline (Lecture 2) CP Asymmetries: sin(2b): the golden measurement the struggle for the other angles Rare decays Penguins are everywhere! Semileptonic decays, decay dynamics, and the magnitudes of CKM elements. Heavy-quark symmetry and Vcb Prospects and future directions A reference: J. Richman, Les Houches lectures, 1997. http://hep.ucsb.edu/papers/driver_houches12.ps (or send e-mail asking for a copy: richman@charm.physics.ucsb.edu) Slide57:  Decay rates for B0(t) and B0 (t) to fCP Calculating the CP Asymmetry:  Calculating the CP Asymmetry If there is just one direct decay amplitude, we will see that If CP violation is due to interference between mixing and one direct decay amp: pure sin(Dm t) time dependence. Calculating l:  Calculating l if just one direct decay amplitude to fCP Piece from mixing (a) Piece from decay Hadronic physics divides out! Calculating l for specific final states:  Calculating l for specific final states Why it is magic:  Why it is magic CP conserving phase! CP violating phase asdf:  asdf Graphical Analysis Analogy: “Double-Slit” Experiments with Matter and Antimatter:  Analogy: “Double-Slit” Experiments with Matter and Antimatter source In the double-slit experiment, there are two paths to the same point on the screen. In the B experiment, we must choose final states that both a B0 and a B0 can decay into. We perform the B experiment twice (starting from B0 and from B0). We then compare the results. CP violation due to interference between mixing and decay: non-exponential decay law:  CP violation due to interference between mixing and decay: non-exponential decay law Ingredients of the CP Asymmetry Measurement:  Ingredients of the CP Asymmetry Measurement Determine initial state: “tag” using other B. Measure Dt dependence Reconstruct the final state system. The Lorentz Boost:  The Lorentz Boost The asymmetric beam energies of PEP-II allow us to measure quantities that depend on decay time. e- 9.0 GeV e+ 3.1 GeV Slide67:  Tagging Leptons : Cleanest tag. Correct 91%, Efficiency 11% Kaons : Second cleanest. Correct 82%, Efficiency 35% b W- c s u d K- W+ b W+ c s u d K+ W- We must classify each neutral B according to whether it “started” as a B0 or a B0. The start time is defined as the decay time of the accompanying B meson (“tag B”). We use flavor-specific final states of the tag B. The Correlated State:  The Correlated State At the Y(4S), the two neutral B mesons evolve as a correlated quantum state until one of them decays. As a consequence, the asymmetry of time-integrated rates is identically zero! At the Y(4S), we must measure the CP asymmetry as a function of time. The experiment would not work with the silicon vertex detector. Slide69:  Acp(Dt) F(Dt) F(Dt) Dt(ps) Dt(ps) sin2b D sin2b Everything perfect  Add tag mistakes  Dilution: D=1-2w Add imperfect Dt resolution Must understand tagging/mistagging and Dt resolution !! Experimental aspects of the sin2b measurement:  Slide70:  Blind Analysis The whole analysis is performed blind. All studies are performed in such a way as to hide information on the value of the final answer. Avoids any subconscious experimenter bias e.g. agreement with the Standard Model! When we are ready, we have an unblinding party….. Slide71:  sin2b (cc) Ks CP = -1 0.76  0.10  0.04 J/Y KL CP = +1 0.73  0.19  0.07 All modes 0.75  0.09  0.04 (stat) (syst) Fit results 56 fb-1: 62 M BB pairs. CP asymmetry in CP -1 and +1 modes:  CP asymmetry in CP -1 and +1 modes J/Y KL CP = +1 Note: likelihood curves are normalized to the total number of tagged events, not B0 and anti-B0 separately. Crosscheck: fit Bflav events as a CP sample:  Crosscheck: fit Bflav events as a CP sample ACP = -0.004  0.027 Expect no CP asymmetry sin2b fit results:  sin2b fit results sin2b (cc) Ks CP = -1 0.76  0.10  0.04 J/Y KL CP = +1 0.73  0.19  0.07 All modes 0.75  0.09  0.04 Systematic errors CP = -1 background 0.019 Dt resolution and detector effects 0.015 Dmd and tB (PDG 2000) 0.014 Monte Carlo statistics 0.014 J/Y KL background 0.013 Signal mistag fractions 0.007 Total systematic error 0.04 (stat) (syst) Fit without |l|=1 constraint (CP=-1 only) |l| = 0.92  0.06 (stat)  0.03 (syst) Iml/|l| = 0.76  0.10 Cross checks:  Cross checks sin2b by decay mode sin2b in sub-samples Individual modes and sub-samples are all consistent. CKM interpretation:  CKM interpretation r h Our sin2b measurement is consistent with current Standard Model constraints from measurements of other parameters. Method as in Höcker et al, Eur.Phys.J.C21:225-259,2001 (also other recent global CKM matrix analyses) Michael Peskin’s viewpoint:  Michael Peskin’s viewpoint Conclusions so far...:  Conclusions so far... We have observed CP violation in the neutral-B meson system. The asymmetry is large, unlike the O(10-3) effects observed in the neutral-K system. The asymmetry displays consistent behavior across all observed channels, including CP odd and CP even final states. The time dependence of the asymmetry agrees with the expectation based on interfering amplitudes involving mixing and direct decay. Conclusions so far...:  Conclusions so far... With the present data sample, the region allowed by the measurement is consistent with the Standard Model CKM framework constrained by CP-violation measurements in K decay non-CP-violating observables in B decay Hadronic Rare B Decays: Towards sin(2a):  Hadronic Rare B Decays: Towards sin(2a) B->pp would measure sin(2a)… …except there is a second direct decay amplitude! Hadronic Rare B Decays: B->p+p-, B->K+p-:  Hadronic Rare B Decays: B->p+p-, B->K+p- B->p+p- B->K+p- mES mES DE DE Mixing and CP Asymmetry Measurement in B->pp:  Mixing and CP Asymmetry Measurement in B->pp Mixing Belle Mixing and Asymmetry Measurement in B->pp:  Belle Mixing and Asymmetry Measurement in B->pp B  K(*)l+l- in the SM and Beyond:  B  K(*)l+l- in the SM and Beyond Flavor changing neutral current (b to s): proceeds via “penguin’’ or box diagrams in the SM. New physics at the EW scale (SUSY, technicolor, 4th generation quarks, etc.) can compete with small SM rate. Complementary to studying b to s g due to presence of W and Z diagrams. Branching Fraction Predictions in the Standard Model:  Branching Fraction Predictions in the Standard Model New Ali et al. predictions lower by 30-40% long-distance contribution from y resonances excluded Decay rate vs. q2 in the SM and SUSY:  Decay rate vs. q2 in the SM and SUSY J/yK y(2S)K q2 q2 SM nonres SM nonres SUSY models Pole from K*g, even in m+m- constructive interf. destructive Generator-level q2 Distributions from Form-Factor Models :  Generator-level q2 Distributions from Form-Factor Models Ali et al. 2000 (solid line) Colangelo 1999 (dashed line) Melikhov 1997 (dotted line) Shapes are very similar! J/y and Large Sideband Control Sample Study: B Likelihood Variable:  J/y Sample: signal-like log LB off resonance J/y and Large Sideband Control Sample Study: B Likelihood Variable Large SB Sample: background-like log LB -10 4 Kl+l- Fit Regions, Unblinded Run 1+2 data (56.4 fb-1) :  Kl+l- Fit Regions, Unblinded Run 1+2 data (56.4 fb-1) DE mES Fit Results (preliminary) :  Fit Results (preliminary) B(BK*ee)/B(BK*mm)=1.21 from Ali, et al, is used in combined K*ll fit. Belle results (29.1 fb-1) :  Belle results (29.1 fb-1) Bkgd shape fixed from MC Results :  Results We obtain the following preliminary results: The statistical significance for B  K l+l- is computed to be > 4s including systematic uncertainties. BaBar and Belle results are both higher than typical theoretical predictions, but the uncertainties are still very large. Measuring Magnitudes of CKM Elements with Semileptonic B Decays:  Measuring Magnitudes of CKM Elements with Semileptonic B Decays Expt. Expt. Need input from theory! Kinematic Configurations in Semileptonic Decay:  Kinematic Configurations in Semileptonic Decay b->cln processes are dominant and are much easier to understand than b->uln decays. reliable theoretical predictions for b->cln at zero recoil (Heavy Quark Symmetry/HQET). zero recoil: b->c without disturbing the light degrees of freedom expansion in LQCD/mQ zero recoil Semileptonic decays: Dalitz plot:  Semileptonic decays: Dalitz plot Effect of V-A coupling on lepton angular distribution and energy spectrum. zero recoil Contributions of different helicities to the rate:  Contributions of different helicities to the rate Zero recoil Max recoil New CLEO measurement of |Vcb |:  New CLEO measurement of |Vcb | CLEO Measurement of |Vcb | : w distribution and extrapolation to zero recoil:  CLEO Measurement of |Vcb | : w distribution and extrapolation to zero recoil Systematic Errors on CLEO |Vcb | Measurement:  Systematic Errors on CLEO |Vcb | Measurement Recent |Vcb | measurements:  Recent |Vcb | measurements Uncorrected for common inputs Corrected for common inputs (Compilation by Artuso and Barberio, hep-ph/0205163, May 2002.) Recent |Vcb | measurements:  Recent |Vcb | measurements Form Factor at Zero Recoil and |Vcb|:  Form Factor at Zero Recoil and |Vcb| The experimental extrapolation to zero recoil velocity of the daughter hadron provides the quantity Zero recoil form factor (“consensus value”) World average |Vcb| Bumps in the road: Crystal Ball observation of the z(8.3) (1984):  Bumps in the road: Crystal Ball observation of the z(8.3) (1984) Photon energy spectrum. First observation of exclusive B decay:  First observation of exclusive B decay CLEO I data (1983) Some free advice :  Some free advice Almost every measurement is very hard, even if it is of a quantity that no one cares about. So, try to find an important measurement that will have real scientific impact. Never determine your event-selection criteria using the same event sample that you will use to measure your signal. Don’t use more cuts than you need. A simple analysis is easier to understand, check, duplicate, and present. Look at all the distributions you can think of for your signal and compare them with what you expect. Look at the distributions of events that you exclude. Do you understand the properties of your background? More free advice :  More free advice When possible, use data rather than Monte Carlo events to measure efficiencies and background levels. Do not use Monte Carlo samples blindly. Find out where the information came from that went into the MC. The MC may do well in someone else’s analysis, but in may never have been checked for the modes or region of phase space relevant to your analysis. Be careful not to underestimate the systematic errors associated with ignorance of signal efficiency background shapes, composition, and normalization Yet more advice:  Yet more advice Don’t be afraid to… ask any question pursue a crazy idea jump into something you don’t already understand question what people say is established fact look into the details and assumptions Conclusions:  Conclusions We have two remarkable new facilities for B physics: KEK-B/Belle PEP-II/BaBar The performance of these accelerators is a major achievement for the laboratories. The clear observation of CP asymmetries in the B meson system is a milestone for particle physics. The measurement of sin(2b) is very well accomodated by the SM. It suggests that the dominant source of CP violation in B decays is due to the CKM phase. In spite of this, we have a long way to go before we have fully tested the SM/CKM framework. Conclusions (continued):  Conclusions (continued) Hadron-collider experiments will soon start to play a major role: the observation and precise measurement of Bs mixing is one of the next major goals. We are just beginning to scratch the surface of rare B decays. They have interesting sensitivity to new physics. The next few years will be very exciting. Backup slides:  Backup slides PEP-II :  PEP-II Very high current, multibunch operation 2 rings helps avoid beam instabilities and parasitic beam crossings (crossings not at the IP) I(e+)=1.3 A (LER), I(e-)=0.7 A (HER) Bunch spacing: 6.3-10.5 ns Beam spot: sx=120 mm sy=5.6 mm sz=9 mm Number bunches/beam: 553-829 (to 1658) High-quality vacuum to keep beam-related backgrounds tolerable for experiments PEP-II/BaBar Construction:  PEP-II/BaBar Construction 1993: Start of PEP-II construction 1994: Start of BaBar construction Summer 1998: 1st e+e- collisions in PEP-II Spring 1999: BaBar moves on beamline May 26, 1999: 1st events recorded by BaBar Oct 29, 2000: PEP-II achieves design luminosity Intense competition with KEK-B/Belle in Japan PEP-II/BaBar :  PEP-II/BaBar The Standard Model predicts O(1) CP asymmetries in B decays! However, these asymmetries occur in processes that are relatively rare, so a large data sample is required. To perform these measurements, a two-ring e+e- storage ring with unequal beam energies was built by SLAC/LBNL/LLNL with unprecedented luminosity. We now have >60 MU (4S) events. The BaBar Collaboration (9 countries):  The BaBar Collaboration (9 countries) BaBar DIRC quartz bar:  BaBar DIRC quartz bar 3.5 cm Overall length (4 bars): 4.9 m No. light bounces (typical)=300 Surface roughness (r.m.s.)= 0.5 nm l (typical) = 400 nm BaBar DIRC Principle:  BaBar DIRC Principle Number of Cherenkov photons=20-60 s(qC) = 3 mrad Experimental aspects of CP measurement:  Acp(Dt) F(Dt) F(Dt) Dt(ps) Dt(ps) sin2b D sin2b True Dt, Perfect tagging: True Dt, Imperfect tagging: Measured Dt, Imperfect tagging: Must measure flavor tag Dilution. D = (1-2w) where w is mistag fraction. Must measure Dt resolution properties. Experimental aspects of CP measurement B0 mixing measurement: D and R(Dt,Dt’):  Amix(Dt) Fmix(Dt) Fnomix(Dt) Dt(ps) Dt(ps) D True Dt, Perfect tagging: True Dt, Imperfect tagging: Measured Dt, Imperfect tagging: B0 mixing measurement: D and R(Dt,Dt’) Amplitude of mixing asymmetry is the dilution factor D. Mixing sample has 10x statistics of CP sample. Shape of Dt determines resolution function R(Dt,Dt’) B->K*g:  B->K*g

Add a comment

Related presentations

Related pages

Jonathan Richman – Wikipedia

Jonathan Richman (* 16. Mai 1951 in Natick bei Boston) ist ein amerikanischer Musiker. Er wurde in den 1970er Jahren als recht verschrobener Singer ...
Read more

Richman (V) - GTA Wiki - Die deutschsprachige ...

Richman ist ein wohlhabender Stadtbezirk von Los Santos in Grand Theft Auto V. Er ist wie Rockford…
Read more

Verdammt lecker | DMAX.de

Vom größten Zimtstern bis zum schärfsten Sushi - Adam Richman, Absolvent der Schauspielschule „Yale School of Drama“, pflegt seit Jahren eine innige ...
Read more

Adam Richman – Wikipedia

Leben . Adam Richman stammt aus einer jüdischen Familie und wuchs in Brooklyn, New York auf. Er ging erst auf die Midwood High School und begann danach ...
Read more

Richman - Wikipedia, the free encyclopedia

Richman as a surname may refer to: Adam Richman (actor) (born 1974), host of the Travel Channel's Man v. Food Adam Richman (singer) (born ca. 1983 ...
Read more

Richman (SA) - GTA Wiki - Die deutschsprachige ...

Eine Villa in Richman. Richman ist auf einem Berg gebaut, weswegen die Bewohner der Villen teilweise auch Ausblick bis nach Downtown haben, sollten nicht ...
Read more

Dima Richman – VBT Wiki

Dima Richman ist ein Rapper mit eigenem und lustigen Style der am VBT 2012, 2013, dem RapSparring teilnahm, so wie aktuell am VBT 2015 teilnimmt.
Read more

Jonathan Richman – laut.de – Band

Porträt laut.de-Biographie Jonathan Richman. Der Song "Roadrunner" ist nur einer von vielen großartigen Rockraketen der Modern Lovers, Jonathan Richmans ...
Read more

3OH!3- Rich Man lyrics - YouTube

3OH!3- Rich Man lyrics horsesRus09. Subscribe Subscribed Unsubscribe 14,375. ... "RICHMAN" by 3OH!3 (Google Play • iTunes • AmazonMP3) Category
Read more

Jonathan Richman | Music Biography, Streaming Radio and ...

Find Jonathan Richman bio, music, credits, awards, & streaming radio on AllMusic - Precocious and goofy singer/songwriter whose work…
Read more