New results from BABAR Brookhaven National Laboratory Particle

New results from BABAR Brookhaven National Laboratory Particle Physics Seminar May 20, 2002 Marie-Hélène Schune Laboratoire de l’Accélérateur Linéaire Orsay, France New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 All numbers are preliminary 1

New results from BABAR • 56 fb-1 I will not talk about – sin 2 b in charmonium modes : sin 2 b = 0. 75 0. 09 0. 04 Winter 2002 conferences 1. 2. BABAR and PEPII Charmless B decays : – B 0 , K or KK – B 0 0 0 3. The “B recoil” physics : – semileptonic branching fractions of B+ and B 0 – D meson production in B decays New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 2

CKM matrix for 3 generations – CKM matrix has 4 real parameters (one phase included) – 2 are well known : • l=|Vus|=sin(q. Cabbibo)=0. 2205 0. 0018 • A =|Vcb|/l 2 =0. 83 0. 06 – unitarity of the CKM matrix leads to constraints that can be tested: h Bd + - , r+ -, … Unitarity Triangle B , r , ln, rln, … Bd Bd, Bd r B D(*)ln, D(*) , … r B D* , DK, K New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 Bd J/y. Ks, D*+D*-, … 3

The BABAR detector 1. 5 T solenoid Cs. I(Tl) EMC e+ (3. 1 Ge. V) DIRC (PID) Drift Chamber Silicon Vertex Tracker e- (9 Ge. V) • • Instrumented Flux Return SVT: 97% efficiency, 15 mm z resol. (inner layers, perpendicular tracks) Tracking : (p. T)/p. T = 0. 13% PT 0. 45% DIRC : K- separation >3 for P<3. 5 Ge. V/c EMC: E/E = 1. 33% E-1/4 2. 1% New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 4

New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 5

PEP-II asymmetric B Factory 9 Ge. V e- on 3. 1 Ge. V e+ : s~10. 58 Ge. V • for B 0 : coherent neutral B pair production and decay (p-wave) • boost of (4 S) in lab frame : b =0. 55 New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 6

Running at the (4 S) PEP-II BABAR Off New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 On 7

B factory performances • May 2 nd : – PEPII delivered : 87 fb-1 – BABAR recorded : 83 fb-1 (including 9 fb-1 off peak ) daily integrated luminosity • results for 55 fb-1 New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 8

2 - Charmless B decays Study of penguins diagrams Possible direct CP violation a • B 0 , K or KK h (r, h) a b r – Branching fractions (aeff a, ) – CP violations measurements (aeff , a ) • B 0 0 0 (aeff a) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 9

B 0 and CP violation (1) Tree amplitude (T) Hadronic Penguin Amplitude (P) BF(B 0 ) << BF(B 0 K ) penguins contributions may be large mixing e-2 ib Tree only : l=hfe 2 ia (a = -b - ) C =0 S =sin(2 a) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 Tree+Peng. C 0 S =sin(2 aeff) 10

B 0 and CP violation (2) f+ : B 0 tag S =0. 7 and C =0. perfect flavour tagging & time resolution New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 realistic mis-tagging & finite time resolution 11

B 0 , K or KK kinematics Axis of “Rest Event” Candidate “Jets” Candidate • Main variables : |cosq. S| – |cosq. S| : angle between the B 0 sphericity axis and the sphericity axis of the rest of the event – F : Fisher discriminant based on “energy flow cones” (CLEO) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 Candidate 12

B 0 , K or KK : m. ES and DE • Energy substituted mass : – dominated by the beam energy knowledge Signal MC ~2. 6 Me. V ~325 Me. V background m. ES • DE : assume mass KK K background – dominated by the tracking resolution (DE)~26 Me. V New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 45 Me. V 13

B 0 , K or KK : the PID (1) The DIRC Quartz bar • Active Detector Surface Measure Angle of Cherenkov Cone in quartz Particle Cherenkov light – Transmitted by internal reflection – Detected by PMTs New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 14

DIRC PMT +light catchers DIRC stand-off box, magnetic shielding and electronic crates New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 15

B 0 , K or KK : the PID (2) • DIRC performances measured on data using D* D 0 and D 0 K (qc) 2. 2 mrad K/ separation 2. 5 p range of 2 -body B decays at BABAR New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 16

B 0 , K or KK : analysis strategy Start with a B 0 h+h- (no PID) m. ES unbinned max L with DE, m. ES, F, q 1 c, q 2 c measure N NK NKK and ~17600 events for ~56 fb-1 5. 24 5. 28 add Dt and tagging information (as for sin 2 b ), fix the yields extract S and C New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 17

B 0 , K or KK : branching fractions results Mode Yield Branching Fraction (10 -6) K Asymmetry (AK ) B 0 + B 0 K- + B 0 K + K Likelihood projections : remove one 1 variable from fit ; cut on L proba B 0 ~83 B 0 m. ES small crossfeed DE New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 B 0 K ~356 B 0 K m. ES small crossfeed DE 18

B 0 , K or KK : BF comparison CLEO 9 fb-1 BABAR 56 fb-1 BELLE 31 fb-1 BF(B 0 + -)(10 -6) 4. 3 1. 6 0. 5 5. 4 0. 7 0. 4 5. 1 1. 1 0. 4 BF(B 0 K- +)(10 -6) 17. 2 2. 5 1. 2 17. 8 1. 1 0. 8 21. 8 1. 5 BF(B 0 K-K+)(10 -6) <1. 9 at 90%CL <1. 1 at 90%CL <0. 5 at 90%CL AK -0. 04 0. 16 -0. 06 0. 05 0. 01 -0. 06 0. 08 0. 01 BF(B 0 ) << BF(B 0 K ) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 19

B 0 , K or KK : CP analyses Dt • Time information Dt : – resolution dominated by Btag vtx ( (Dz) ~ 180 mm) – extracted from data Breco sample (D(*) , D(*)r, D(*)a 1…) – Background shape : side bands Similar to sin(2 b) analyses New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 20

B Flavour tagging methods Hierarchical, mutually exclusive, tagging categories For electrons, muons and kaons use the charge correlation l - n b W- D, D* d b c B 0 d W- c W+ s K B 0 d Lepton Tag Multivariate analysis exploiting the other kinematic information of the event, e. g. , Neural Network Each category is characterized by the probability of giving the wrong answer (mistag fraction w) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 d Kaon Tag NN output Not Used Ø Momentum spectrum of the charged particles Ø Information from non-identified leptons and kaons Ø Soft from D* decay *0 21 0) Prob(B

B 0 , K or KK : CP analyses tagging • Split the events into 4 tagging categories : – – leptons kaons NT 1 NT 2 m. ES leptons NN type tagging kaons • Performances obtained on data (Breco sample) Similar to sin(2 b) analyses New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 NT 1 NT 2 22

B 0 , K or KK : CP analyses validation • Validation : measure t. B on /K sample : t. B=1. 66 0. 09 ps • Validation : measure Dmd Select the K events and plot Amix Dmd=0. 517 0. 062 ps-1 New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 23

B 0 , K or KK : CP analyses results S =-0. 01 0. 37 0. 07 S [-0. 66, +0. 62] at 90 % CL C =-0. 02 0. 29 0. 07 C [-0. 54, +0. 48] at 90 % CL ~9 Background ~27 B 0 Select the B 0 events Plot the asymmetry between B 0 tag and B 0 tag events ~25 B 0 New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 24

(r, h) constraints from S and C BBNS: QCD FACTORISATION APPROACH: M. Beneke, G. Buchalla, M. Neubert and C. T. Sachrajda Nucl. Phys. B 606 (2001) 245 CKM Fitter H. Höcker, H. Lacker, S. Laplace and F. Le Diberder Eur. Phys. J. C 21 225 -259 (2001) http: //ckmfitter. in 2 p 3. fr/ New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 25

B 0 , K or KK : CP comparisons Belle (K Trabelsi Moriond): -C (BABAR) A c 2(S , C )=9 (~2. 5 ) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 26

Search for B 0 0 0 • BF(B 0 0 0) : – measured isospin analysis to get a from B 0 + (M. Gronau, D. London Phys Rev Lett. 65 3381 -3384 (1990)) – upper bound still a useful constraint: (Y. Grossman, H. Quinn Phys Rev D 58 017504 (1998)) • Experimentally challenging : – low BF expected (th. predictions : 10 -7 - few 10 -6) – purely neutral final state • Recent results : Yield limit (10 -6) (90% CL) CLEO (9 fb-1) 6. 2+4. 8 -3. 7 5. 7 BELLE (30 fb-1) 12 6 5. 6 New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 27

Search for B 0 0 0 : analysis (1) Axis of “Rest Event” Candidate “Jets” Candidate F • Main variables : – |cosq. S| : angle between the B 0 sphericity axis and the sphericity axis of the rest of the event – F : Fisher discriminant based on the “energy flow cones” – m. EC : energy constrained mass – DE = E*B – s/2 in the CMS New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 28

Search for B 0 0 0 : analysis (2) • The B r 0 background : – event shape similar to the signal one – m. EC only slightly wider (small missing) – DE is the only discriminating variable – in the fit : fix BF(B r 0)=2. 410 -5 (from CLEO upper limit) B r 0 -. 4 -. 2 0 . 2 B 0 0 0 . 4 DE (Ge. V) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 -. 4 -. 2 0 . 2 . 4 DE (Ge. V) 29

Search for B 0 0 0 : results • Unbinned maximum L fit using F PDF and (m. EC , DE ) PDF • Compare with an optimized cut and count analysis : • Fit yield : Main systematics : • neutral efficiency • continuum m. EC param. • F param. • B r 0 yield BF(B 0 0 0) < 3. 4 10 -6 at 90 % CL New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 54 fb-1 30

3 - The “B recoil” physics generic B decay B type known should allow (in principle !) to measure all B BF Will show : leptonic studies D 0 and D production New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 31

The “B recoil” physics • B factories : the world’s largest sample of reconstructed B mesons Nsignal=13743 125 56 fb-1 Reconstruct the Cabibbo-favored hadronic decays : B 0 sample Nsignal=12909 120 B+ sample New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 32

Inclusive semileptonic B decays • Inclusive rate is large – Sides of the unitarity triangle |Vcb| and |Vub| a (r, h) b (0, 0) (1, 0) – B Xcen is large – B Xuen is an experimental challenge New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 33

Inclusive semileptonic B decays • Compare b+/b 0 with t(B+)/t(B 0) : • Extract the prompt and cascade lepton spectrum from the charge correlation with the Breco : – B- Xce-n – B+ Xce+n – B 0 : correct for mixing CLEO results (2. 4 fb-1) using B 0 tagged sample and (4 S) l : – b 0 = (10. 78 0. 60 0. 69)% – b+ = (10. 25 0. 57 0. 65)% – b+/b 0 = New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 34

Electron identification • Variables : – E/p – Shower shapes – DCH and DIRC • Performances measured on data: 90% • Backgrounds : - conversions - 0 dalitz decays 10 -3 -J/ decays p (Ge. V) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 35

Background subtracted electrons spectra Right sign Wrong sign B N right sign= N+p results on 21 fb-1 B 0 Nright sign=N 0 p(1 -cd)+N 0 ccd Nwrong sign=N 0 pcd+N 0 c(1 -cd) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 36

b 0 and b+ results B+ • BF results : B 0 ratio : b+/b 0=. 950 . 080 . 091 b+/b 0=. 99 . 10 . 03 New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 37

D production in B decays • Inclusive branching fractions of B 0 and B+ to charmed hadrons – Enters in the nc (= mean charm per B decay ) computation s D 0, D-, Ds-, Lc-, … WRONG b B 0 or B- c c q D 0, D+, Ds+, Lc+, … RIGHT • For each B specie two measurements are performed : ( ) • The absolute BF : BF(B DX) with D = D 0 or D+ – “large statistics” – Need e(D) from MC • The wrong D ratio : – Wrong D sample statistically limited – Need to correct for mixing for the B 0 – More MC independant New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 38

D production in B decays reconstruction Semileptonic: B 0 D* l n Hadronic : – B 0 D* , D*r, D*a 1 fit to cosq. B-D*l variable 50 fb-1 m. ES cosq. B-D*l • D reconstruction : D 0 K and D K New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 39

( ) BF(B DX) • Fit N(D) and correct for Brec background BF(B DX) Brec : B 0 D*ln M(K ) ( ) BF(B 0 D 0 X)(%) Semilep. 57. 1 3. 3 4. 6 Hadronic 59. 3 5. 9 3. 9 Combined 57. 9 2. 1(*) 3. 5(**) M(K ) Brec : B 0 D* , D*r, D*a 1 BF(B 0 D X)(%) Semilep. 35. 7 2. 8 3. 9 Hadronic 35. 3 4. 3 3. 8 Combined 35. 6 2. 3 1. 1(*) 3. 6(**) (*) M(K ) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 (**) Correlated syst. Uncorrelated syst. 40

w(D) for neutral B mesons • Correlate the D and the B flavours : – For B 0 : should correct for mixing cobs = Mix+Unmix = cd + w (1 - 2 cd) • done on an optimized time interval (|Dt|<2. 5 ps) reduced statistical uncertainty, Dmd dependance w( B 0 D 0 X ) (%) Brec : B 0 D*ln Brec : B 0 D* , D*r, D*a 1 Unmix Semilept. 15. 9 3. 5 2. 4 Hadronic 9. 6 4. 7 1. 1 Combined 13. 1 2. 8 1. 5 0. 6 w( B 0 D X) (%) Mix Semilept. 7. 3 3. 7 1. 9 Hadronic 8. 9 7. 1 1. 8 Combined 7. 7 3. 3 1. 4 0. 8 M(K ) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 41

D production in B decays • Results suggest B 0 spectator quark effect negligible in wrong D production • Results consistent with world data (“B admixture”) BF( B 0 D 0 X ) BF( B 0 D+ X) BF( B 0 D- X) = = ( 50. 3 3. 0 3. 7 ) % ( 7. 6 1. 7 1. 1 ) % ( 32. 8 2. 5 3. 5 ) % ( 2. 7 1. 2 0. 6 ) % 30 or 51 fb-1 Compare BF( B 0 D 0 + D+ X) = (83. 1 6. 4) % with world data: BF( Badmixt D 0 + D+ X) = (78. 5 3. 4) % • In the future : – Add the B sample – 100 fb-1 – start to look for Ds and Lc (looser Breco selection ? ) Better understanding of the overall picture of the B decays New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 42

• A true factory of B mesons : Summary – BF(B 0 + -) = (5. 4 0. 7 0. 4) 10 -6 – BF(B 0 K+ -) = (17. 8 1. 1 0. 8) 10 -6 Unfortunately not enough to get B 0 0 0 – BF(B 0 0 0) < 3. 4 10 -6 at 90 % CL • CP violation results : – S =-0. 01 0. 37 0. 07 – C =-0. 02 0. 29 0. 07 • “B recoil” physics is starting : – Semi leptonic measurements – D mesons production in B decays BF( B 0 D 0 X ) BF( B 0 D+ X) BF( B 0 D- X) New results from BABAR, Marie-Hélène Schune, BNL, May 20 th 2002 = = ( 50. 3 3. 0 3. 7 ) % ( 7. 6 1. 7 1. 1 ) % ( 32. 8 2. 5 3. 5 ) % ( 2. 7 1. 2 0. 6 ) % 43