Figure 1: Elevation view of the BABAR Detector.

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1 BABAR F. Anulli (Art. 23), R. Baldini Ferroli, A. Calcaterra, L. Daniello (Tecn.), R. de Sangro, G. Finocchiaro, S. Pacetti (Bors. PD), P. Patteri, I. Peruzzi (Ass., Resp.), M. Piccolo, M. Rama, A. Zallo 1 Introduction BABAR has run at the SLAC asymmetric B-factory PEP-II till April 2008; the physics program of BABAR is centered on, but not limited to, the study of the CP violation in the decay of neutral B mesons. The B system is the best suited to study CP violation because the expected effects are large, appear in many final states and, most importantly, can often be directly related to the Standard Model parameters. The datasample collected at the Υ(4S) resonance has allowed significant advances in a large number of topics in B, charm and tau lepton physics; all three angles of the Unitarity Triangle have been measured, direct CP violation has been observed in B decays, several new B decay modes have been measured, and new charmed states have been discovered. JKZKIZUX) 2 (7>4,*3.( (-.23*> 2&,3*9.(8-.*1) +47).7( ':(0.3,(4.1 9IGRK ('('8)UUXJOTGZK9_YZKS _ ^ ` S /6.3897:2*39*) +1:=7*9:73.+7 '&77*1 8:5*7(43):(9.3, (4.1 *1*(9742&,3*9.( (&147.2*9*7 *2( )7.+9(-&2'*7 )(- 8.1.(43;*79*= 97&(0*7 8;9 (-*7*304; )*9*(947 ).7(.+7 *3)(&5 +47<&7) *3)51:, K K ',2558 Figure 1: Elevation view of the BABAR Detector. The PEP-II asymmetric e + e collider has operated mainly at a center-of-mass energy of GeV corresponding to the mass of the Υ(4S) resonance, which decays 50% in B + B and 50% in B 0 B 0. The electron beam of 9.0 GeV collides head-on with the positron beam of 3.1 GeV resulting in a Lorentz boost (βγ = 0.56) to the Υ(4S) resonance, making possible the measurement of the time-dependent CP violation of the neutral B s. The PEP-II operations stopped in April 2008 after a budget cut has shortened the original schedule.

2 The BABAR detector (Fig. 1) has been designed primarily for CP violation studies, but it has also served well for the other physics objectives of the experiment. The asymmetry of the beam energies is reflected in the detector design: the apparatus is centered 37 cm ahead of the collision point, along the direction of the high-energy beam, to increase forward acceptance. Charged particles are detected and their momenta measured with the combination of a five-layer silicon vertex tracker (SVT) and a 40-layer drift chamber (DCH), both operating in a 1.5 T solenoidal magnetic field. Photons are detected by a CsI(Tl) electromagnetic calorimeter that provides high detection for energies above 20 MeV. Charged particle identification is provided by the ionization loss measurements in the SVT and DCH, and by an internally reflecting ring-imaging Cherenkov detector covering the central region of the detector. Muons and neutral hadrons are identified in the iron magnet s yoke, where a total thickness of 65 cm of Fe plates has been segmented and instrumented with Resistive Plate Counters and Limited Streamer Tubes. This system is called Instrumented Flux Return, or IFR. 2 Activity As a consequence of the budget cut to the US HEP field in 2008, the BABAR data taking was reduced to about three months (from January to April 6) as opposed to the previously planned ten months. Since running at the Υ(4S) for just three months would have determined a modest relative increase of the overall Υ(4S) sample, it was decided to make the best use of the data collected by BABAR by running at center-of-mass energies corresponding to the Υ(3S) and Υ(2S) resonances, and by scanning the energy region between and GeV. While the Upsilon meson and its excited states were discovered over twenty years ago, little was actually known about the potentially rich spectroscopy of bottomonium. In particular, key states predicted by the Standard Model, such as the ground state η b or the h b, had never been observed before. In addition, heavy quarkonium is an excellent place to search for new physics effects. Scanning energies above the Υ(4S) is important to search for bottomonium-like exotic states that would give indications on new forms of aggregation states not fitting the ordinary interpretation of quark-antiquark bound states. With these motivations BABAR collected fb 1 at the Υ(3S) (10 8 Υ(3S) decays), fb 1 at the Υ(2S) (10 8 Υ(2S) decays) and a total of 3.9 fb 1 scanning the energy range between and GeV. The integrated luminosity as function of time is reported in Fig. 2. The major result is the first observation of the bottomonium ground state, the η b, performed by BABAR and published in [18]. Besides the study of bottomonium states, the analysis activity by BABAR in 2008 continued covering a very wide spectrum of measurements, including updates on the angles of the Unitarity Triangle β, α, γ, branching ratios and CP-violation of rare B decays, V ub, V cb, the extensive study of charm and τ decays (BABAR is also a charm and τ factory), and the most extensive systematic study up to now of low-energy meson spectroscopy in the energy range between 1 and 4 GeV, possible at BABAR using the technique of Initial State Radiation (ISR). A total of 41 papers were published in the same year on major journals and Babar continued as a major contributor at all HEP Conferences In the next sections the analysis items which led to publications in 2008 and in which the Frascati group is more directly involved are shortly described.

3 ] As of 2008/04/11 00:00 As of 2008/04/11 00:00-1 Integrated Luminosity [fb BaBar Run 1-7 PEP II Delivered Luminosity: /fb BaBar Recorded Luminosity: /fb BaBar Recorded Y(4s): /fb BaBar Recorded Y(3s): 30.23/fb BaBar Recorded Y(2s): 14.45/fb Off Peak Luminosity: 53.85/fb Delivered Luminosity Recorded Luminosity Recorded Luminosity Y(4s) Recorded Luminosity Y(3s) Recorded Luminosity Y(2s) Off Peak ] -1 Integrated Luminosity [fb BaBar Run 7 PEP II Delivered Luminosity: 56.82/fb BaBar Recorded Luminosity: 54.00/fb BaBar Recorded Y(4s): 0.78/fb BaBar Recorded Y(3s): 30.22/fb BaBar Recorded Y(2s): 14.45/fb Off Peak Luminosity: 8.54/fb Delivered Luminosity Recorded Luminosity Recorded Luminosity Y(4s) Recorded Luminosity Y(3s) Recorded Luminosity Y(2s) Off Peak /12/ /12/ /12/ /01/ /01/ /01/ /01/ /02/ /02/ /02/ /02/ /03/ /03/ /03/ /03/ /03/ /04/06 Figure 2: Left: BABAR integrated luminosity from the start of the data taking in 1999 till the end of PEP-II operations in Right: BABAR integrated luminosity in Run7 collected between December 2007 and April The group has also been active in participating to the Design Study for a detector at the SuperB Factory, a proposed e + e asymmetric collider with 100 times more luminosity than PEP-II. More details are given in Section 5. 3 Measurement of the angle γ with B ± D ( )0 K ( )± decays The measurement of the angle γ of the Unitarity Triangle using the B D ( )0 K ( ) decays with D 0 K 0 S h+ h (h = π, K) has been performed. This family of decay channels gives the most precise measurement of γ among the methods which have been explored so far. Our result, based on a data sample of B B, is γ = (76 ± 22(stat) ± 5(syst) ± 5(model)) (Fig. 3). The third uncertainty comes from the model assumptions for the Dalitz plots of the flavour-tagged D 0. Details on the analysis technique can be found in the journal article which has been published in Phys. Rev. D in 2008 [29]. 4 Light hadron spectroscopy with initial state radiation events Initial state radiation (ISR) events can be effectively used to measure e + e annihilation at a high luminosity storage ring, such as the B-factory PEP-II. A wide mass range is accessible in a single experiment, contrary to the case of fixed energy colliders, which are optimized only in a limited energy region. In addition, the broad-band coverage may result also in greater control of systematic effects because only one experimental setup is involved. Measurements of the main hadronic final states in the energy range between thresholds and 6 GeV have been carried out at BABAR. Besides the study of the KKπ and KKη final states [41], we are now finalizing the analysis of various K S K L π + nπ 0 channels, with one, two and three additional π 0 s.

4 1 - CL ± ± B DK ± ± B D*K ± ± B DK* Combined σ 2σ γ (deg), Figure 3: α = 1 CL as a function of γ for B D 0 K, B D 0 K, and B D 0 K decays separately, and their combination, including statistical and systematic uncertainties and their correlations. The dashed (upper) and dotted (lower) horizontal lines correspond to the oneand two-standard deviation intervals, respectively. 4.1 Unexpected threshold behavior in baryon-antibaryon cross sections Recent BABAR data on baryon-antibaryon cross sections show an unexpected threshold behavior. In particular the cross sections for e + e pp, ΛΛ, Σ 0 Σ 0, and ΛΣ 0 have monotonically decreasing behaviors starting from the threshold, where they take non vanishing values, up to about 4 GeV. Generally the baryon-antibaryon cross section should be zero at threshold due to the vanishing of the phase space. In the pp case the phase space vanishing is cancelled by the Coulomb correction. Moreover, using such a correction we get a unitary normalization for the common proton form factor at the production threshold, i.e. for time-like square momentum q 2 = (2M p ) 2 [a1]. Also in the case of e + e Λ c Λ c, as recently measured by Belle for the first time, a pointlike behavior is suggested for the charmed charged baryon, being the form factor at threshold G Λc (4M 2 Λ c ) 1, even if within a large error [a2]. The same argument can not be used in the case of neutral baryons, where the non-vanishing cross section at threshold is interpreted as a remnant of quark pair Coulomb interaction before the hadronization, taking into account the asymmetry between attractive and repulsive Coulomb factors. A complete study of the other crucial channels: Σ + Σ and ++ is underway. In the first case we expect a cross section which, after correcting for the p Σ + mass difference, should behave like the pp one, showing the Coulomb threshold enhancement. In the case of ++, instead, the Coulomb enhancement should play a dominant role at the production threshold, being stronger by a factor of four, with respect to typical charge +e baryons.

5 5 The SuperB project A conceptual design report of a next generation asymmetric-energy e + e collider (SuperB) capable of delivering about 100 times the luminosity of the current B factories has recently been compiled [sb1]. This report discusses the physics motivation, detector, and accelerator designs for the next generation B factory at an e + e collider R&D for the SuperB Drift Chamber In 2007 the BABAR Frascati group has started the R&D activities that lead towards the design and construction of the tracking detector for the SuperB. Since the BABAR drift chamber has performed excellently throughout the course of the experiment, we chose it as the baseline design for the SuperB tracking detector. However, at a luminosity of at least cm 2 s 1 we expect the occupancy in the drift chamber volume, especially in the forward region, to be considerably higher than in BABAR. The gas mixture and the cell shape need therefore to be optimized for faster operation. As a general consideration the BABAR design of the drift chamber did not emphasize low mass end-plates, so this would be the typical area of improvement. We envisage an all-carbon Fiber conical or dome shaped structure to minimize the material in front of the outer detector components. The engineering of the front-end electronics also needs complete rework. As mentioned in the previous paragraphs, experimental activities were started during 2008: an external tracker to measure space time relations in different gases and spatial resolution in prototype devices was refurbished and is being commissioned. A dedicated small dimension prototype has been designed and engineered, once built it will be exposed to cosmic rays and to the Frascati BTF to experimentally check simulation results obtained with MAGBOLTZ and/or GARFIELD. 5.1 Development of Simulation Tools for Detector Design and Physics Studies The design of the SuperB detector and the study of the physics reach of the experiment require specific simulation tools. Depending on the nature of the study, a detailed simulation (Geant4) or a fast simulation is needed. The Frascati group has been involved in the development of both tools. Three different GDML models of the drift chamber (differing on the endplates shape) have been implemented and plugged into the Geant4 simulation of the machine interaction region and the detector to study the hit rates from Touschek, radiative Bhabha and e + e e + e e + e background events. This is the first step of a study which aims at designing the drift chamber layout to keep the background rates down to an acceptable level. To optimize the overall SuperB detector geometry and to study the reach of the main physics channels, a simulation tool which is both highly flexible in the detector description, and very fast, is needed. These requirements are not met by a detailed simulation based on Geant4. For this reason a fast Monte Carlo (FastSim) was developed, which includes a simplified detector element description (cylinders, rings, cone,...), a full modeling of particle passage through the detector (energy loss, multiple scattering, showering,...), the parameterization of the detector response (track hit resolution, cluster shape, Cherenkov ring resolution,...) and particle reconstruction

6 (tracks, clusters, photon rings,...). In addition FastSim has been designed in such a way that the output is compatible with the BABAR analysis tools (vertexing, tagging, etc.). The Frascati group is coordinating the development of the SuperB fast simulation and of the physics tools. 5.2 Detector Geometry Working Group The SuperB detector as described in the Conceptual Design Report (CDR) [sb1] has a number of options not yet defined that have a large impact on the overall detector geometry. A Detector Geometry Working Group (DGWG) has been setup at the end of 2008 to study the physics tradeoffs of the open CDR detector options with the goal of being able to finalize the global geometry and define the subsystems of the SuperB detector. The DGWG will help evaluating the impact of several detector options and designs, such as a) a forward PID detector compared to a longer drift chamber (DCH), b) a backward EM calorimeter vs. no backward EM calorimeter, c) the internal geometry of the Silicon Vertex Tracker (SVT), d) the SVT-DCH transition radius, e) the distribution and amount of absorber in the muon system. The Frascati group is co-coordinating the DGWG. 6 Talks at Conferences in 2008 G. Finocchiaro, CKM unitarity triangle: mixing and CP violation, presented at the Second Workshop on Theory, Phenomenology and Experiments in Heavy Flavour Physics, June , Capri, Italy. S. Pacetti, Charmed Particles Production in e + e cc at 10.6 GeV presented at the Workshop on parton fragmentation processes in the vacuum and in the medium, February 25-29, 2008, ECT Trento, Italy. S. Pacetti, Initial state radiation at BaBar presented at the Workshop on parton fragmentation processes in the vacuum and in the medium, February 25-29, 2008, ECT Trento, Italy. S. Pacetti, Mesoni leggeri e fattori di forma del nucleone a BaBar presented at the Mini- Workshop sulle prospettive di Fisica adronica al Jefferson Lab e in altri laboratori, February 27-29, 2008, Genova, Italy. S. Pacetti, Unexpected features of e + e baryon-antibaryon cross sections near threshold Hadron Electromagnetic Form Factors Workshop, May 12-23, 2008, ECT Trento, Italy. S. Pacetti, Unexpected features of e + e baryon-antibaryon cross sections near threshold and analysis of G p E /Gp M presented at the Hadron Structure and QCD: from LOW to HIGH energies, June 30 - July 4, 2008, Gatchina, Russia. P. Patteri, Initial state radiation physics at BABAR and Belle, presented at the Workshop on Hadron Structure and QCD 2008, June 30 - July 4, Gatchina, Russia.

7 7 BABAR Publications in 2008 References 1. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett. 102, (2009). 2. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 79, (2009). 3. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 4. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 5. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 6. B. Aubert et al. [BaBar Coll.], Phys. Rev. D , (2008., 7. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 8. B. Aubert et al. [The BaBar Coll.], Phys. Rev. D 78, (2008). 9. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett (2008), 10. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 11. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 12. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett. 102, (2009). 13. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett. 101, (2008). 14. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 15. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 16. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 17. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 18. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett. 101, (2008), Erratum ibid. 102, (2009). 19. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 20. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett (2008). 21. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 22. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett. 101, (2008). 23. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett. 101, (2008). 24. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 79, (2009). 25. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008).

8 26. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 27. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 79, (2009). 28. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 29. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 30. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 31. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett. 101, (2008). 32. B. Aubert et al. [BaBar Coll.], Phys. Rev. Lett. 101, (2008). 33. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 34. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 35. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 77, (2008). 36. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 37. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 77, (2008). 38. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 77, (2008). 39. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 78, (2008). 40. B. Aubert et al. [BaBar Coll.], Phys. Rev. D 77, (2008). 41. B. Aubert et al. [BaBar Coll.], arxiv: , accepted by Phys. Rev. D. Other publications related to BABAR a1. R. Baldini, S. Pacetti, A. Zallo, and A. Zichichi, Eur. Phys. J. A 39, 315 (2009). a2. R. Baldini, S. Pacetti, and A. Zallo, arxiv: SuperB publications sb1. The SuperB Conceptual Design Report, arxiv: sb2. Proceedings of the SuperB Workshop VI, January , Valencia, Spain, arxiv: