Search

This work is supported by DOE and NSF (USA), NSERC(Canada), CEA and CNRS-IN2P3 (France), BMBF andDFG (Germany), INFN (Italy), FOM (Netherlands), NFR (Norway), MES (Russia), MICIIN (Spain), and STFC(United Kingdom). Individuals have received support fromthe Marie Curie EIF (European Union), the A. P. Sloan Foundation (USA), and the Binational Science Foundation(SA-Israel).

We study the Υ(1S) radiative decays to γπ^+π^− and γK^+K^− using data recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e^+e^− collider at center-of-mass energies at the Υ(2S) and Υ(3S) resonances. The Υ(1S) resonance is reconstructed from the decay Υ(nS)→π^+π^−Υ(1S), n=2, 3. Branching fraction measurements and spin-parity analyses of Υ(1S)radiative decays are reported for the I=0 S-wave and f_2(1270) resonances in the π^+π^− mass spectrum, the f′_2(1525) and f_0(1500) in the K^+K^− mass spectrum, and the f_0(1710) in both.

The Mu2e experiment at Fermilab searches for the charged-lepton flavour violating (CLFV) conversion of a negative muon into an electron in the field of an aluminum nucleus, with a distinctive signature of a mono-energetic electron of energy slightly below the muon rest mass (104.967 MeV). The Mu2e goal is to improve by four orders of magnitude the search sensitivity with respect to the previous experiments. Any observation of a CLFV signal will be a clear indication of new physics. The Mu2e detector is composed of a tracker, an electro- magnetic calorimeter and an external veto for cosmic rays surrounding the solenoid. The calorimeter plays an important role in providing particle identification capabilities, a fast online trigger filter, a seed for track reconstruction while working in vacuum, in the presence of 1 T axial magnetic field and in an harsh radiation environment. The calorimeter requirements are to provide a large acceptance for 100 MeV electrons and reach at these energies: (a) a time resolution better than 0.5 ns; (b) an energy resolution < 10% and (c) a position resolution of 1 cm. The calorimeter design consists of two disks, each one made of 674 undoped CsI crystals read by two large area arrays of UV-extended SiPMs. We report here the construction and test of the Module-0 prototype. The Module-0 has been exposed to an electron beam in the energy range around 100 MeV at the Beam Test Facility in Frascati. Preliminary results of timing and energy resolution at normal incidence are shown. A discussion of the technical aspects of the calorimeter engineering is also reported in this paper., 8 pages, 16 figures, submitted to IEEE

The processes $e^+e^-\to K^0_{\scriptscriptstyle S}K^\pm\pi^{\mp}\pi^0$ and $e^+e^-\to K^0_{\scriptscriptstyle S}K^\pm\pi^{\mp}\eta$ are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb$^{-1}$ data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from $K^{*0}(K\pi)^0$, $K^{*}(892)^\pm(K\pi)^\mp$ and $K^0_{\scriptscriptstyle S}K^\pm\rho^{\mp}$ are studied. The $J/\psi$ is observed in all of these channels, and corresponding branching fractions are measured.

The Mu2e experiment at Fermilab looks for Charged Lepton Flavor Violation (CLFV) improving by 4 orders of magnitude the current experimental sensitivity for the muon to electron conversion in a muonic atom. A positive signal could not be explained in the framework of the current Standard Model of particle interactions and therefore would be a clear indication of new physics. In 3 years of data taking, Mu2e is expected to observe less than one background event mimicking the electron coming from muon conversion. Achieving such a level of background suppression requires a deep knowledge of the experimental apparatus: a straw tube tracker, measuring the electron momentum and time, a cosmic ray veto system rejecting most of cosmic ray background and a pure CsI crystal calorimeter, that will measure time of flight, energy and impact position of the converted electron. The calorimeter has to operate in a harsh radiation environment, in a 10-4 Torr vacuum and inside a 1 T magnetic field. The results of the first qualification tests of the calorimeter components are reported together with the energy and time performances expected from the simulation and measured in beam tests of a small scale prototype., Comment: 11 pages, 7 figures, proceedings of 14th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD16) 3 - 6 October 2016 Siena, Italy, Journal of Instrumentation, Volume 12, January 2017 http://stacks.iop.org/1748-0221/12/i=01/a=C01061

We report on an analysis of $\tau^-$ decaying into $\omega\pi^-\nu_\tau$ with $\omega\to\pi^+\pi^-\pi^0$ using data containing nearly 320 million tau pairs collected with the BABAR detector at the PEP-II asymmetric energy $B$-Factory. We find no evidence for second-class currents and set an upper limit at 0.69% at a 90% confidence level for the ratio of second- to first-class currents.

We present a Scan Method analysis of the allowed region of the rho bar - eta bar plane using the latest input measurements of the CKM matrix elements, sin 2 beta, B0(s,d) mixing, epsilon(K), alpha and gamma. In this approach, we make no assumptions as to the distribution of theory uncertainties; rather, we scan over the range of plausible theoretical uncertainties and determine confidence level contours in the rho bar eta bar plane. We determine alpha from branching fraction and CP asymmetry measurements of B decays to all light pseudoscalar-pseudoscalar, pesudoscalar-vector, vector-vector and a1-psudoscalar mesons and determine gamma from D(*)K(*), D(*) pi and D rho modes, thereby including correlations between the angles of the unitarity triangle. We parametrize the individual decay amplitudes in terms of color-allowed tree, color-suppressed tree, gluonic penguin, singlet penguin, electroweak penguin, as well as W-exchange and W-annihilation amplitudes. Our procedure accounts for all correlations among the fitted CKM parameters (rho bar, eta bar, A, lambda). The data are consistent with the Standard Model with no need for new physics contributions. We also examine example "wall plots", i.e., projections of sensitive parameters showing correlations among them and regions of preferred theoretical parameters., 8 pages, 8 figures, To appear in the proceedings of the 50 years of CP violation conference, 10 -- 11 July, 2014, held at Queen Mary University of London, UK

The subject of determining the significance of observations in particle physics is discussed. Several dangers are identified, all related to the problem of knowing the sampling probability distribution. Techniques for mitigating these pitfalls are presented.

The experimental status concerning the two new narrow states with charm-strange content is reviewed. The states have masses of 2317 and 2460 MeV, widths less than 10 MeV, isospin consistent with zero, and spin-parities consistent with being 0^+ and 1^+, respectively. Although the masses are lower than the conventional expectation, these states appear to be the j=1/2 P-wave levels of the D_s system, where j is the light quark angular momentum; there may be mixing with the j=3/2 level for the 1^+ state., Comment: 4 pages, 10 figures LaTeX; To appear in Proceedings of the International Europhysics Conference on High Energy Physics, July 17-23, 2003, Aachen. A (long file) version with some clearer figures may be found at: http://www.hep.caltech.edu/~fcp/papers/eps03.pdf This version updates version 1 with a correction to labelling of Fig. 8 (Thanks to U.Karshon for noticing this)

Caltech High Energy Physics (HEP) has a broad program in both experimental and theoretical physics. We are known for our creativity and leadership. The future is uncertain and we strive to be involved in all the major areas of experimental and theoretical HEP physics so no matter where the important discoveries occur we are well positioned to play an important role. An outstanding group of postdoctoral scholars, graduate students, staff scientists, and technical and administrative personnel support our efforts in experimental and theoretical physics. The PI’s on this grant are involved in the following program of experimental and theoretical activities: I) EXPERIMENTAL PHYSICS Our CMS group, led by Harvey Newman and Maria Spiropulu, has played a key role in the discovery and interpretation of the Higgs boson and in searches for new physics. They have important hardware responsibilities in both ECAL and HCAL and are also involved in the upgrades needed for the High Luminosity LHC. Newman's group also develops and operates Grid-based computing, networking, and collaborative systems for CMS and the US HEP community. The charged lepton (Mu2e) and quark BaBar flavor physics group is led by David Hitlin and Frank Porter. On Mu2e they have been instrumental inmore » the design of the calorimeter. Construction responsibilities include one third of the crystals and associated readout as well as the calibration system. They also will have responsibility for a major part of the online system software. Although data taking ceased in 2008 the Caltech BaBar group is active on several new forefront analyses. The neutrino group is led by Ryan Patterson. They are central to NOvA's core oscillation physics program, to calibration, and to detector readiness being responsible for the production and installation of 12,000 APD arrays. They have key roles in neutrino appearance and disappearance analysis in MINOS and MINOS+. Sunil Golwala leads the dark matter direct detection effort. Areas of activity include: CDMS II data analysis, contributions to SuperCDMS Soudan operations and analysis, R&D towards SuperCDMS SNOLAB, development of a novel screener for radiocontamination (the BetaCage), and development of new WIMP detector concepts. Ren-Yuan Zhu leads the HEP crystal laboratory for the advanced detector R&D effort. The crystal lab is involved in development of novel scintillating crystals and has proposed several crystal based detector concepts for future HEP experiments at the energy and intensity frontiers. Its current research effort is concentrated on development of fast crystal scintillators with good radiation hardness and low cost. II) THEORETICAL PHYSICS The main theme of Sergei Gukov's current research is the relation between the geometry of quantum group invariants and their categorification, on the one hand, and the physics of supersymmetric gauge theory and string theory, on the other. Anton Kapustin's research spans a variety of topics in non-perturbative Quantum Field Theory (QFT). His main areas of interest are supersymmetric gauge theories, non-perturbative dualities in QFT, disorder operators, Topological Quantum Field Theory, and non-relativistic QFT. He is also interested in the foundations and possible generalizations of Quantum Mechanics. Hirosi Ooguri's current research has two main components. One is to find exact results in Calabi-Yau compactification of string theory. Another is to explore applications of the AdS/CFT correspondence. He also plans to continue his project with Caltech postdoctoral fellows on BPS spectra of supersymmetric gauge theories in diverse dimensions. John Preskill works on quantum information science. This field may lead to important future technologies, and also lead to new understanding of issues in fundamental physics John Schwarz has been exploring a number of topics in superstring theory/M-theory, supersymmetric gauge theory, and their AdS/CFT relationships. Much of the motivation for these studies is the desire to gain a deeper understanding of superstring theory and M-theory. The research interests of Mark Wise span particle physics, cosmology and nuclear physics. His recent work has centered on extensions of the standard model where baryon number and lepton number are gauged and extensions of the standard model that have novel sources of baryon number violation and new sources of charged lepton flavor violation« less

We present results of a unitary triangle fit based on the scan method. This frequentist approach employs Gaussian uncertainties for experimental quantities, but makes no arbitrary assumptions about the distribution of theoretical errors. Instead, we perform a large number of fits, scanning over regions of plausible theory errors for each quantity, and retain those fits meeting a specific confidence level criterion, thereby constraining the $\bar \rho - \bar \eta $ plane using the standard input measurements (CKM matrix elements, $\sin2 \beta, B^0_{d,s}$ mixing, $\epsilon_K$) as well as branching fraction and \CP asymmetry measurements of B decays to $PP, PV, VV$, and $a_1 P$ final states to determine $\alpha$, $D^{(*)}K^{(*)}$ modes to determine $\gamma$, and $D^{(*)}\pi$ and $D\rho$ modes to determine $2\beta +\gamma$. We parameterize individual decay amplitudes in terms of color-allowed tree, color-suppressed tree, penguin, singlet penguin, electroweak penguin, as well as $W$-exchange and $W$-annihilation amplitudes. With this parameterization, we obtain a good fit to the measured branching fractions and \CP asymmetries within the Standard Model {\it ansatz}, with no new physics contributions. This simultaneous fit allows us to determine the correlation between $\alpha$ and $\beta$ as well as between $\gamma$ and $\beta$., Comment: 10 pages, 8 figures, version uploaded to Phys. Rev. D

The Beijing Spectrometer (BES) detector is a general purpose solenoid detector at the Beijing Electron Positron Collider (BEPC) in Beijing, China, that has collected large numbers of J/ψ, ψ′, Ds, D and τ events. In this paper, we describe the recent upgrade of the initial BES detector (BESI) to the improved BESII detector.

We search for the decay Υ(1S)→γA^0, A^0→gg or ss , where A^0 is the pseudoscalar light Higgs boson predicted by the next-to-minimal supersymmetric Standard Model. We use a sample of (17.6±0.3)×10^6 Υ(1S) mesons produced in the BABAR experiment via e^+e^-→Υ(2S)→π^+π^-Υ(1S). We see no significant signal and set 90%-confidence-level upper limits on the product branching fraction B(Υ(1S)→γA^0)·B(A^0→gg or ss) ranging from 10^(-6) to 10^(-2) for A^0 masses in the range 0.5–9.0 GeV/c^2.

The general properties of two commonly-used methods of interval estimation for population parameters in physics are examined. Both of these methods employ the likelihood function: (i) Obtaining an interval by finding the points where the likelihood decreases from its maximum by some specified ratio; (ii) Obtaining an interval by finding points corresponding to some specified fraction of the total integral of the likelihood function. In particular, the conditions for which these methods give a confidence interval are illuminated, following an elaboration on the definition of a confidence interval. The first method, in its general form, gives a confidence interval when the parameter is a function of a location parameter. The second method gives a confidence interval when the parameter is a location parameter. A potential pitfall of performing a likelihood analysis without understanding the underlying probability distribution is discussed using an example with a normal likelihood function.

We study the Upsilon(3S,2S)->eta Upsilon(1S) and Upsilon(3S,2S)->pi+pi- Upsilon(1S) transitions with 122 million Upsilon(3S) and 100 million Upsilon(2S) mesons collected by the BaBar detector at the PEP-II asymmetric energy e+e- collider. We measure B[Upsilon(2S)->eta Upsilon(1S)]=(2.39+/-0.31(stat.)+/-0.14(syst.))10^-4 and Gamma[Upsilon(2S)->eta Upsilon(1S)]/Gamma[Upsilon(2S)-> pi+pi- Upsilon(1S)]=(1.35+/-0.17(stat.)+/-0.08(syst.))10^-3. We find no evidence for Upsilon(3S)->eta Upsilon(1S) and obtain B[Upsilon(3S)->eta Upsilon(1S)] eta Upsilon(1S)]/Gamma[Upsilon(3S)->pi+pi- Upsilon(1S)]

A preliminary measurement of the branching fraction B ( τ − → K S 0 π − ν τ ) is made using 384.6 fb−1 of e + e − collision data provided by the PEP-II collider, operating primarily at s = 10.58 GeV , and recorded using the BaBar detector. From this we measure: B ( τ − → K ¯ 0 π − ν τ ) = ( 0.840 ± 0.004 ( stat ) ± 0.023 ( syst ) ) % . This result is the most precise measurement to date and is consistent with the world average.

The potential to probe the Standard Model and beyond with studies in the B-meson system has resulted in the investigation of techniques to perform this physics. One of the most promising is to produce the Υ(4S) resonance, moving in the laboratory frame, using an e^+e^- storage-ring collider with different energies in the two beams. In April 1989, a workshop was held at Caltech to investigate the issues involved in designing such an accelerator. I summarize the results of that workshop in this paper: and also investigate some parametric questions incorporating several of the constraints discussed there. The purpose of the Caltech Workshop was to consider the accelerator physics issues faced in attempting to achieve a high-luminosity (ℒ ~ 10^(34) cm^(-2) s^(-1)) asymmetric e^+e^- storage-ring B-factory in the E_(cm) ≈ 10-GeV region. There were four working groups, chosen to address what were perceived to be the most difficult areas: (1) beam-beam limitations, (2) optics, (3) beam current limitations, and (4) small beam pipe at the interaction point (IP). I summarize the conclusions from each of these groups in the following sections. Many of these considerations apply as well to symmetric B-factory colliders.

Several approaches to testing the hypothesis that two histograms are drawn from the same distribution are investigated. We note that single-sample continuous distribution tests may be adapted to this two-sample grouped data situation. The difficulty of not having a fully-specified null hypothesis is an important consideration in the general case, and care is required in estimating probabilities with ``toy'' Monte Carlo simulations. The performance of several common tests is compared; no single test performs best in all situations., 35 pages, 15 figures, 5 tables. Plain TeX. Uses graphicx external package. For better quality figures, go to: http://www.hep.caltech.edu/~fcp/statistics/hypothesisTest/PoissonConsistency/PoissonConsistency.pdf

Data taken by the Mark II detector at the SLAC {ital e}{sup +}{ital e}{sup {minus}} storage ring PEP was used to search for exclusive decays of {ital D}{sup {plus minus}} and {ital B}{sup {plus minus}} mesons into two charged leptons plus a charged pion or kaon. All possible charge and lepton combinations consistent with charge conservation were considered and no evidence for any signals was found. We obtain upper limits for the various branching ratios ranging from 2.5{times}10{sup {minus}3} to 9.2{times}10{sup {minus}3}, at a 90% confidence level. Some of these limits can be used to constrain leptoquark masses in various models.

We report upon the present status of global fits to Cabibbo-Kobayashi-Maskawa matrix., Comment: 3 pages, 3 figures invited talk presented at EPS conference, Aachen July 17-23

There is now a rapidly growing body of experimental data relevant to the question of whether the standard model CKM quark mixing matrix is a correct description of \CP-violation as well as of non--\CP-violating flavor decay processes. In the detailed comparisons with theoretical predictions that are required to investigate this, a key challenge has been the representation of non-statistical uncertainties, especially those arising in theoretical calculations. The analytical procedures that have been used to date require procedural value judgments on this matter that color the interpretation of the quantitative results they produce. Differences arising from these value judgments in the results obtained from the various global CKM fitting techniques in the literature are of a scale comparable to those arising from the other uncertainties in the input data and therefore cannot be ignored. We have developed techniques for studying and visualizing the sensitivity of global CKM fits to non-statistical uncertainties and their parameterization, as well as techniques for visual evaluation of the consistency of experimental and theoretical inputs that minimize the implicit use of such value judgments, while illuminating their effects. We present these techniques and the results of such studies using recently updated theoretical and experimental inputs, discuss their implications for the interpretation of global CKM fits, and illustrate their possible future application as the uncertainties on the inputs are improved over the next several years., Contributed paper to International Europhysics Conference On High-Energy Physics (HEP 2003) and to International Symposium On Lepton And Photon Interactions At High Energies (LP03)

Several proposals are being developed around the world for an e+e- linear collider with an initial center of mass energy of 500 GeV. In this paper, we will discuss why a project of this type deserves priority as the next major initiative in high energy physics.

Nonminimal neutral Higgs bosons decaying into a muon pair were searched for using the Mark II detector at the SLAC ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ collider PEP at \ensuremath{\surd}s =29 GeV. A neutral scalar Higgs boson ${H}_{s}^{0}$ can be produced accompanied by a pseudoscalar neutral Higgs boson ${H}_{p}^{0}$ via a virtual ${Z}^{0}$. If the mass of one of the Higgs bosons is between the muon pair threshold and the kaon pair threshold, it may decay predominantly into a muon pair. We looked for muon pair+jet(s) [${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ \ensuremath{\rightarrow}${H}_{s}^{0}$${H}_{p}^{0}$\ensuremath{\rightarrow}${\ensuremath{\mu}}^{+}$${\ensuremath{\mu}}^{\mathrm{\ensuremath{-}}}$+qq\ifmmode\bar\else\textasciimacron\fi{} (${\ensuremath{\tau}}^{+}$${\ensuremath{\tau}}^{\mathrm{\ensuremath{-}}}$)] and three-muon-pair [${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${H}_{s}^{0}$${H}_{p}^{0}$\ensuremath{\rightarrow}3 (${H}_{p}^{0}$)\ensuremath{\rightarrow}3(${\ensuremath{\mu}}^{+}$${\ensuremath{\mu}}^{\mathrm{\ensuremath{-}}}$)] topologies. We found no evidence for these signals above the known background level, and we obtained limits on \ensuremath{\Gamma}(${Z}^{0}$\ensuremath{\rightarrow}${H}_{s}^{0}$${H}_{p}^{0}$) as a function of the Higgs-boson masses.

The Mark II detector has been upgraded in preparation for its role as the first detector to take data at the Stanford Linear Collider. The new detector components include the central drift chamber, the time-of-flight system, the coil, the endcap electromagnetic calorimeters and the beam energy and luminosity measuring devices. There have also been improvements in detector hermeticity. All of the major components were installed for a test run at the PEP storage ring (√s = 29 GeV) in 1985. This paper describes the upgraded detector, including its trigger and data acquisition systems, and gives performance figures for its components. Future improvements are also discussed.

A double gap of cylindrical proportional chambers has been designed and built for use with a large solid angle, modular NaI(Tl) array (The Crystal Ball). The chambers are constructed of three coaxial foam-epoxy shells, covered with an aluminum-mylar laminate. One of the high voltage cathodes in each chamber has been photo-etched to produce a pattern of stripes and precise position measurements of tracks passing transverse to the chamber axis are found by pulse height analyzing the shaped and amplified induced strip signals. Performance of the chamber using both the strip signals and the sense wire readout is presented. The design of both the signal handling electronics and the digital portions of the systems is discussed.

Diffractive dissociation of neutrons and N ∗ production are studied in the reaction π − n → π − π − p at 15 GeV/ c . The reaction is dominated by a broad, low-mass diffractive enhancement in the pπ − mass. Evidence is presented for the production of at least one N ∗ resonance in the mass region 1.4–1.8 GeV. Comparison with ISR data suggest that this N ∗ resonance is produced by pomeron exchange. The N ∗ production occurs predominantly at t ′ > 0.1 GeV 2 which suggests a different coupling from the usual diffractive reactions. The non-resonant diffractive background is compared with a double-Regge model and the statistical dissociation model.