BaBar ventures into the non B-physics world : R from ISR and Pentaquark Searches Nicolas Berger, SLAC For the BaBar Collaboration

Nicolas Berger, Cornell Seminar 2 Outline Measuring R –Why ? –Why use ISR ? –Exclusive Analyses –Inclusive Analysis Search for Pentaquarks –Motivation –  +  pK 0 S –  5   –  5   K NOT shown here: Many More related analyses: –inclusive  c,  c, ,  studies –inclusive ,K,p spectra, –studies of fragmentation models –DsJ, X(3870) –Searches for charmed pentaquarks,  and more!

Hadronic Cross-sections from Initial-state Radiation

Nicolas Berger, Cornell Seminar 4 Fit SM parameters using as inputs: –W, Z parameters (M W,  W M Z,  Z,  Had 0, R l, A FB 0,l ) –Leptonic asymmetries (A l (P  ), A l (SLD)) –Heavy flavors (R X, A X, A FB 0,X, X=b,c) –Weak Mixing Angle (sin 2  eff lept (Q FB Had )   sin 2  W (NuTeV/E158), Q W (Cs)) –m t,  Had (5) (M Z 2 ). Results globally consistent Can measure m H indirectly (loop effects) Motivation(1) : Standard Model Fits (0.21) 2 (0.12) 2 (0.04) 2 (0.10) 2 (0.13) 2 Not the largest contribution to the error since BES 2002 results but still large! All observables except NuTeV F. Teubert, ICHEP 2004 low-Q 2 data now excluded

Nicolas Berger, Cornell Seminar 5 Hadronic Contributions to   (q 2 =0) is the most precisely measured constant of nature, but we need  (M Z 2 ) => “Run”  to M Z 2 Ward identity: only the vacuum polarization contributes -- Hadronic part ? Contour integral (Analyticity): Optical theorem (Unitarity):  Had = 4m  2 Im s Re s s0s0 2 Born cross-section Hadrons

Nicolas Berger, Cornell Seminar 6 Motivation(2) : Hadronic Contributions to (g-2)  Units of Pure QED Electroweak Corrections Hadronic Vacuum Polarization (LO) e + e -     Hadronic VP (HO) Light-by-Light Scattering Kinoshita, Nio hep-ph/ Czarnecki et al. hep-ph/ ) Davier, Hoecker, Eidelman and Zhang hep-ph/ Hagiwara et al. hep-ph/ Melnikov, Vainshtein hep-hp/ aa 11,658, aa exp  3.6 rad 5.0 exp  0.8 rad  2.8 SU(2) Contributions to the Standard Model (SM) Prediction: Can be expressed as a dispersion integral for R(s) Total SM Prediction for e + e - (hep-ph/ ) : BNL 2004 Measurement (hep-ph/ ) : 2.5  discrepency! “QED kernel” function (closed form)

Nicolas Berger, Cornell Seminar 7 Experimental Status for R,  QED and a   s [GeV] Hagiwara et al. (2003) Davier et al. (2003) Error due to radiative corrections Same integral form for a  and  QED. low-s region crucial for a .  QED sensitive to full accessible range

Nicolas Berger, Cornell Seminar 8 Recent Progress in R Measurements BES hep-ex/ KLOE hep-ex/ CMD-2 : E. Solodov, Talk at ICHEP 2004 (Variable beam Energy) ISR Method Untagged photons (outside calorimeter)

Nicolas Berger, Cornell Seminar 9 The BaBar Detector BaBar DCH 40 layers, axial and stereo wires. Covers 92% of solid angle  p t /p t ~ % Particle ID up to 600 MeV/c BaBar EMC: 6580 CsI(Tl) crystals Covers 91% of solid angle but inner rings degraded by beam background. E resolution ~2 % at high E. BaBar DIRC Quartz Cherenkov radiator Covers 80% of solid angle Particle ID above 600 MeV/c BaBar SVT 5 double-sided Si layers Vertex Reconstruction, Tracking Hit resolution  m

Nicolas Berger, Cornell Seminar 10 BaBar Particle ID Cherenkov Angle (Kaon from D* -  D 0  , D 0  K -  + sample) All Events

Nicolas Berger, Cornell Seminar 11 PEP-II Luminosity PEP-II is an asymmetric e + e - collider with a CM energy of GeV. Peak luminosity = cm -2 s -1 Integrated luminosity = 244 fb -1. Analyses presented here use fb -1.

Nicolas Berger, Cornell Seminar 12 ISR at  (4S) Energies Hadrons e+e+ e-e- Hard photon: E  * = GeV at  s’ = 0-7 GeV.  No beam-gas events High event fiduciality with cuts on  polar angle Hadronic system collimated by recoil. Harder spectrum  better detection efficiency.  Reduced dependence on had. model. ISR/FSR separation –FSR contribution is expected to be small, well separated from ISR –Separated with angular analysis. Mass resolution –Limited by photon E resolution –Exclusive analyses : excellent results from kinematic fits. –Not a problem for  had.

Nicolas Berger, Cornell Seminar 13 MC Studies KKMC Born cross- section: “Radiator function” (LO) KKMC event generator s’<8 GeV 15.3 <   < o  total = 90.2 pb   = 18.7 pb In 200 fb -1, N total = 18 million N  = 3.7 million 5.7M d  /ds’ [pb/2.5 MeV] 2.6M 3.8M (  : 3.5 M)  s’ [GeV] BES 2002: ~250K events KKMC Events In 200 fb -1 :  s’ [GeV] Triggering Efficiencies Level 1 Level 3 “BG Filter” = Level 4

Nicolas Berger, Cornell Seminar 14 Overview of Exclusive Analyses Common features –Perform kinematic fits with constraints : E,p conservation Resonance masses –Use fit   to discriminate signal and background. –Use particle Identification to select/reject kaons and protons In solid boxes presented here, in dashed boxes in progress. +-+- +-+-+-00+-+-+-00 +-+- +-0+-0 K+K-K0SK0LK+K-K0SK0L K+K-+-K+K-K+K-K+K-+-K+K-K+K- K + K -  K 0 K   0  pp J/  DD*

Nicolas Berger, Cornell Seminar 15 e + e -   +  -  +  -  Perform kinematic fits with m  = 0 for 4 , 2K2 , 4K hypotheses –Accept events with good  2. –Reject if good   in “neighbor” modes –For 4  mode,  2 4  10 Identify kaons using Cherenkov angle and dE/dx. Normalize cross-sections w.r.t e + e -   +  -  events/0.025 GeV   (~60K evts) data ISR Background e + e -   +  -  +  - cross-section (89.3 fb -1)    Non-ISR Background MC Covers entire spectrum Signal MC data Non-ISR Background MC Average BG fractions

Nicolas Berger, Cornell Seminar 16 f 2 (1270) or f 0 (1370) ? Resonant Structures in e + e -   +  -  +  -  M   (GeV/c 2 ) Assuming PDG values for B(J/   ),  (J/  2S)  ee): J/  +  -  +  -  (2S)  J/      +  - PDG: 31.0  2.8 % PDG: (4.0  1.0) Charmonium states not included in MC   a2a2  (2S) excluded from these plots Would be interesting to compare with J/  0  0 BF from e + e -   +  -  0  0 ... Work in progress! M 4  = GeV MC Data

Nicolas Berger, Cornell Seminar 17 e + e -  K + K -  +  -  Require 1 or 2 Kaon IDs  2 2K2  30,  2 4K > 20. Negligible background Good agreement with DM1, higher E CM reach. Systematics: Kaon ID, Efficiency. e + e -  K + K -  +  - cross-section (89.3 fb -1 ) PDG: (7.2  2.3) Assuming PDG value of  (J/   ee):

Nicolas Berger, Cornell Seminar 18 e + e -  K + K -  +  -  Resonant Structures K*(892) K  dominates Little K*K* ,  in K + K - and     spectra with K*(892) bands excluded Hint of  f 0 (980),  f 0 (600) ? Excluding the K*(892) bands  band   K* 0

Nicolas Berger, Cornell Seminar 19 e+e-  K+K-K+K-e+e-  K+K-K+K- e + e -  K + K - K + K - cross-section (89.3 fb -1 ) Require 3 or 4 Kaon IDs  2 4K 20 Negligible background First measurement ever of the e + e -  K + K - K + K -  cross- section. Dominated by systematics: –Particle ID –Luminosity –Tracking efficiency –Acceptance losses Assuming PDG value of  (J/   ee): PDG: (7.0  3.0) No large  signal

Nicolas Berger, Cornell Seminar 20 e + e -  J/    +  -  Require E,p balance, 1C fit with m  = 0. Backgrounds mostly ISR processes, use muon ID. Get  J/  from ratio of peak to continuum events. BABAR 88.4 fb -1 In agreement with world average + better error. e + e -   +  -   ~ MeV With PDG values for B(J/     ) and B(J/  e + e - ): Cross-section given by: ISR luminosity at s’=m 2

Nicolas Berger, Cornell Seminar 21 e + e -   +  -  0  New results (Summer 2004): –Measurement of 3pi form factor on a wide energy range –Measurement of B(J/  3  4C fit requiring E,p conservation,  0 mass (using photon angles but not energy) Backgrounds from –e + e -  K + K -  0 , e + e -  n  –e + e -  qq   +  -  0  0 –Background level : % in ,  regions Rises to 15-50% at higher masses Known to ~25% below 2 GeV Detection efficiency ~10%, weak dependence on M 3 . Mass resolution: 6, 7, 9 MeV/c 2 at , , J/  masses. Events/0.01 GeV/c 2 higher  ’s ? BaBar 124 fb -1 Solid: Signal MC Points: data e + e -  K + K -  0  e+e-  +-00e+e-  +-00

Nicolas Berger, Cornell Seminar 22   Structures in e + e -   +  -  0  Fit the  mass region, including  ’ and  ’’ Fix relative phases to  -  : (163  7)   -  : 180   -  : 0  Assume PDG values for    . We get: fit  2 /d.o.f = 146/148 PDG: (6.35  0.11)% PDG: (4.59  0.14)%   PDG: MeV/c 2 PDG : MeV PDG: 1670 ± 30 MeV/c 2 PDG: 315 ± 35 MeV

Nicolas Berger, Cornell Seminar 23 e + e -   +  -  0  J/  and Cross-Section PDG: (1.50  0.20)%BES 2003: (2.10  0.12)% N J/  = 920  34 Using  (J/   ee)= 5.61  0.20 keV from the e + e -  J/    +  -  results, we have: From  J/ , we extract: DM2 BaBar Preliminary SND Cross-Section: Overall normalization error ~5% below 2.5 GeV. Consistent with SND data for M 3  < 1.4 GeV. Inconsistent with DM2 results.

Nicolas Berger, Cornell Seminar 24 Inclusive ISR Analysis Goal : extract  Had to 3-4 % between 0-7 GeV. ISR Selection –Require unmatched cluster with E CM > 3 GeV –s’ given by E . Efficiency –Triggering efficiency ~98%, can be calibrated to below 1%. –Photon fiducial detection inefficiency ~10%, can be calibrated to few % level. –Weak dependence on hadronization model. Luminosity –Extracted from standard  (4S) luminosity using MC prediction for the “radiator function”. –Uncertainty on  (4S) luminosity ~ 1%, and < 1% for MC calculations (KKMC generator).

Nicolas Berger, Cornell Seminar 25 s’ [GeV 2 ] Smeared spectrum (All Clusters) MC Spectrum Energy resolution ~3%, affects the spectrum, especially at low s’. However, we measure integrals of R(s)/s, not R(s)/s itself: Smearing  events move in s’; Problem only if weight function is non-uniform. –OK for  Had –Does not work for a  Energy Resolution effects s’ [GeV 2 ] Smeared spectrum (Crystal Centers)  s’ [GeV] E  [GeV] MC spectrum Smeared spectrum (Crystal centers) Smeared spectrum (All clusters)

Nicolas Berger, Cornell Seminar 26 Event Selection Remove QED background: –Radiative Bhabhas –e + e -   including   e + e - –Virtual Compton scattering Keep e + e -   substract MC prediction –Must retain high efficiency –Problems for  e modes but branching fractions well known. Significant backgrounds from e + e -  uu,dd   X and e + e -     X, with  0 faking an ISR photon. Reject using –Explicit  0 veto (if other photon found) –Shower shape cuts (for “merged  0 ” case) –Event Shape cuts Fiducial Efficiency After QED Veto After  0 Veto Sufficient purity can be obtained up to  s’~ 6 GeV with efficiency ~80% of fiducial  cc, uds   Before  0 veto After  0 veto Signal (KKMC) s’ [GeV] Efficiency

Pentaquark Searches

Nicolas Berger, Cornell Seminar 28 Experimental Overview New, exotic resonances observed: –  + : seen nK or pK decays by many experiments –     /  0 : seen by NA49 –  c : A charmed partner to  + seen by HERA However, many negative results as well:  + : CDF, HyperCP, E690, HERA-B, Aleph, Delphi…  : CDF, E690,HERA-B, WA49 NA49 CLAS Inclusive Many sightings, but masses don’t agree…

Nicolas Berger, Cornell Seminar 29   -  dss(dd,ss)  -- Theory Overview Several models predict a 10+8 multiplet of SU(3) f for non-charm pentaquarks (doesn’t include HERA’s  C + ) A 27 multiplet also possible (  ++ ) Assume J = ½. In red, states covered in this talk. In green, searches not shown here  +  ududs   K-K- K+K+ N 5 +  uud(dd,ss)  N 5 0  udd(dd,ss)  pK 0 S K0SK0S   - -  sdsdu    0  uss(dd,ss)    +  ususd    +  uus(dd,ss)    0  uds(dd,ss)    -  dds(dd,ss)  pK 0 S ++ B(  5 --  -  - ) < 50%: =  - K -, also  … B(  +  pK 0 S ) = 25% –50% for pK 0 /nK + –50% K 0 S /K 0 L Searches in  K only sensitive to octet states BFs to  K depend on 10-8 mixing  model-dependent N 5 may be below  K threshold ++  K 0 S

Nicolas Berger, Cornell Seminar 30 Hadron Production Rates in e+e- Look at multiplicity of hadrons per spin state in e + e - collision events. Weak dependence on quark content, spin,… Strong dependence on mass Pentaquarks may not be too different from other hadrons. Normalizing to  (1520) may not be a good idea.

Nicolas Berger, Cornell Seminar 31 Search for  +  pK 0 S cc BaBar 123 fb -1 Proton selection using dE/dx and Cherenkov, clean over wide momentum range. Use K 0 S   +  -. Expected Resolution on  + mass ~ 2 MeV, would be most precise so far. Can also look for  5 +. Large signal for  c +  pK 0 S Better resolution for  + since near threshold  c+ c+

Nicolas Berger, Cornell Seminar 32 Search for  +  pK 0 S (and  5 + ) 0.0 < p* < 0.5 GeV/c  = 1 MeV:  < % c.l.  = 8 MeV:  < % c.l. 3.5 < p* < 4.0 GeV/c Events / 2 MeV/c 2  5 +  pK 0 S  + (1540) ? ? ? ++  55 B(  +  pK 0 S ) = 25% taken into account

Nicolas Berger, Cornell Seminar 33 Search for  +  pK 0 S :  c + Signal M(pK 0 S ) [GeV/c 2 ] 100K  C ’s in data sample Resolution 5-7 MeV 3.5 < p* < 4.0 GeV/c 0.0 < p* < 0.5 GeV/c M(pK 0 S ) [GeV/c 2 ] c+c+

Nicolas Berger, Cornell Seminar 34 Search for  5 0/--   -  ±  *(1530) cc     BaBar 123 fb-1 Look for inclusive production of :     BaBar 123 fb-1 Apply loose particle ID on proton Use displaced vertices: –c  (  ) = 7.9 cm, –c  (  -) = 4.9 cm Select masses near the nominal  and  - masses Control particles: –  * 0 (1530)   -  + –  c 0 (2470)   -  +

Nicolas Berger, Cornell Seminar 35 Search for  5 --   -  - Exotic channel  No features No sign of the NA49 particle  = 1 MeV:  < % c.l.  = 18 MeV:  < % c.l.     BaBar 123 fb-1  5 —- (1862) Limits on  B(  5 --  -  - )

Nicolas Berger, Cornell Seminar 36 Search for  5 0   -  + :  5 0,  * 0 and  c 0 N  *  5000  =7.3 MeV/c 2 N  c  2000  =9.3 MeV/c 2  *(1530) 123 fb -1  *(1530) cc  5 0 (1862)     BaBar 123 fb-1

Nicolas Berger, Cornell Seminar 37 Search for N 5 /  5   K  p  [GeV]   [GeV] Look at K = K +,K -,K 0 S  K only sensitive to octet states, not antidecuplet Require tight proton selection. For  and K 0 S, cut on angle between flight direction and momentum direction. Backgrounds mostly real  and K  0 K searches also performed for  0   can probe antidecuplet, but more BG (soft photon).  K0SK0S

Nicolas Berger, Cornell Seminar 38 Search for  5 0   K 0 S  K 0 S 123 fb-1 N  c    = 5.9 MeV  C fb -1 C0C0  5 0 (1862)  = 1 MeV:  < % c.l.  = 18 MeV:  < % c.l. Limits on  B(  5 0  K 0 S )

Nicolas Berger, Cornell Seminar 39 Search for  5 -   K -  K  123 fb -1 N    = 3.0 MeV   123 fb -1  = 1 MeV:  < % c.l.  = 18 MeV:  < % c.l.

Nicolas Berger, Cornell Seminar 40 Search for N 5 +   K + N  c   = 5.3 MeV  c  123 fb -1 c+c+  c + feed-down  K  123 fb -1 We have B(  c +  K + ) = B(  c +  +  0 ) = 3.6% B(  c +  K + K 0 ) = 0.6% So modes with particles missing/mis-ID’d can have large contributions.

Nicolas Berger, Cornell Seminar 41 Searches in   K Modes Bottom line: Less clean than  K, same features, no Pentaquarks no  below threshold K-K- K-K- K+K+ K+K+ K0SK0S K0SK0S

Nicolas Berger, Cornell Seminar 42 Results in Perspective Assume –B(  +  pK 0 S ) = 25% –B(  5 --  -  - ) = 50% Assume pentaquarks from udsc, not bb No model-independent results for  K, since BFs not known Limits can be placed with respect to other baryons. Limits stand below expectations for: –  5 + by a factor of 8-15 –   -- by a factor of 4-6

Nicolas Berger, Cornell Seminar 43 Conclusions Promising prospects for ISR at BaBar –Coverage of wide energy ranges –Advantageous kinematics, radiative corrections situation. Many Exclusive ISR channels already measured; more in progress (  ’, pp, KK…). Inclusive ISR analysis can provide a precise measurement of  Had. Several analyses of inclusive hadronic spectra are in progress. Pentaquark searches have yielded negative results so far. However, they have highlighted potential for study of charmed and non-charmed Baryons.

Backup Slides

Nicolas Berger, Cornell Seminar 45 e+e-  +-+-e+e-  +-+-

Nicolas Berger, Cornell Seminar 46 e+e-  +-+-e+e-  +-+-

Nicolas Berger, Cornell Seminar 47 2K 2  Structures

Nicolas Berger, Cornell Seminar 48 More 2K 2  Structures All Events Events with the other K  combination in the K* band.