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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Status of the JLab Eta Factory (JEF) experiment

The JLab Eta Factory (JEF) experiment is designed to study various decays of the ? meson using the GlueX detector in Hall D at Jefferson Lab. The experimental program includes measuring the Dalitz distribution from ???+???0 to determine the up/down quark mass difference, looking for evidence for new C-violating/P-conserving physics, providing input to higher-order chiral perturbation theory calculations, and searching for evidence of dark matter. The latter two items rely on measuring the rare ???0?? decay mode that will require an upgrade to the existing GlueX equipment, which is a fixed target apparatus based on a 2-Tesla solenoid magnet. Charged tracks are reconstructed using drift chambers within the magnet and neutral particles are detected in the forward direction in the Forward Calorimeter (FCAL), an array of lead glass blocks. The JEF program calls for replacing the ?80×80 cm2 region of the FCAL around the beam line with an array of 2×2×20 cm3 lead tungstate crystals. The status of this upgrade will be presented.

Taylor, Simon↗
DOE OSTI2011

Rare Leptonic B and B to S L+ L- Decays at B-Factories

We review recent results from the BABAR and Belle experiments on rare electroweak B-meson decays, with emphasis on those occuring through flavor changing neutral current interactions of the type b {yields} s{ell}{bar {ell}}. The recent results include measurements of the isospin asymmetry and lepton forward-backward asymmetry in B {yields} K*{ell}{sup +}{ell}{sup -} decays from BABAR, a search for B {yields} {pi}{ell}{sup +}{ell}{sup -} from Belle, and searches for B {yields} K{sup (*)} {nu}{bar {nu}} from BABAR. We also briefly review the status of B{sup 0} {yields} {ell}{sup +}{ell}{sup -} and B{sup +} {yields} {ell}{sup +}{nu} searches.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Charm and Charmonium Spectroscopy at BaBar

In the last few years many new unexpected new particles have been discovered in the analysis of B-factories data. In the charm sector, the newly discovered D{sub s} mesons are difficult to explain within potential models. In the charmonium sector, the large variety of new states are difficult to accommodate in the quark model and some of them are candidates for being hybrids or 4-quark states. Results will be presented on charm and charmonium spectroscopy from BaBar experiment using inclusive e{sup +}e{sup -} interactions, B decays and exclusive ISR reactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Model-Independent Results for the Decay B \to L Nu(L) Gamma at BaBar

We present a search for the radiative leptonic decays B{sub +} {yields} e{sup +} {nu}{sub e}{gamma} and B{sup +} {yields} {mu}{sup +}{nu}{sub {mu}}{gamma} using data collected by the BABAR detector at the PEP-II B factory. We fully reconstruct the hadronic decay of one of the B mesons in {Upsilon}(4S) {yields} B{sup +}B{sup -} and then search for evidence of the signal decay within the rest of the event. This method provides clean kinematic information on the signal's missing energy and high momentum photon and lepton, and allows for a model-independent analysis of this decay. Using a data sample of 465 million B-meson pairs, we obtain sensitivity to branching fractions of the same order as predicted by the Standard Model. We report a model-independent branching fraction upper limit of {Beta}(B{sup +} {yields} {ell}{sup +}{nu}{sub {ell}}{gamma}) < 15.6 x 10{sup -6} ({ell} = e or {mu}) at the 90% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Measurement of the D - s Decay Constant f Ds and Observation of New Charm Resonances Decaying to D*π

The absolute branching fractions for the decays D - s → ℓ-$\bar{v}$ - (ℓ = e, μ, or τ) are measured using a data sample corresponding to an integrated luminosity of 521 fb -1 collected at center of mass energies near 10.58 GeV with the BABAR detector at the PEPII e + e - collider at SLAC. The number of D s - mesons is determined by reconstructing the recoiling system DKXγ in events of the type e + e - → DKXD* s - , where D* s - → D s - γ and X represents additional pions from fragmentation. The D s - → ℓ - v ℓ events are detected by full or partial reconstruction of the recoiling system DKX{gamma}ℓ. The following results are obtained: β(D s - → μ - v) = (6.02 ± 0.38 ± 0.34) x 10 -3 , {Beta}(D s - → τ - v) = (5.00 ± 0.35 ± 0.49) x 10 -2 , and B(D s - → e - ν) < 2.8 x 10 -4 at 90% C.L., where the first uncertainty is statistical and the second is systematic. The branching fraction measurements are combined to determine the D s - decay constant f Ds = (258.6 ± 6.4 ± 7.5) MeV. In addition, a study has been performed of the D + π} - , D 0 π} + , and D* + π - systems in inclusive e + e - → c c interactions in a search for excited D meson states. The dataset used consists of {approx}454 fb -1 . The mass spectra for these systems show, for the first time, candidates for the radial excitations of the D 0 , D* 0 , and D* + , as well as the L = 2 excited states of the D 0 and D - , where L is the orbital angular momentum of the quarks. Finally, a prototype of a next generation Detector of Internally Reflected Cherenkov radiation (Focusing DIRC) has been tested using a 10 GeV electron beam at SLAC. The Focusing DIRC is based on the DIRC which was used in the BABAR detector, but has new pixel photon detectors which improve the resolution on the single photon time of propagation by about an order of magnitude allowing, for the first time, to correct the chromatic smearing in the Cherenkov angle. The Focusing DIRC may be used in a future Super-B factory.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Charmonium Spectroscopy (X,Y,Z) at the B Factories

Since 2003 several states in the charmonium mass region were discovered. While in the conventional c{bar c} spectrum some states are missing, the number of states observed up to now is larger than empty spaces in the c{bar c} spectrum. This, together with other difficulties to explain observed states as a c{bar c} mesons triggered discussions on a possible exotic interpretations. In this proceedings we present current experimental status from B-factories of the so called X, Y and Z states.

Experiment-HEP,HEPEX↗
DOE OSTI2025

Lead tungstate calorimeter of the Jefferson Lab Eta Factory experiment

A new electromagnetic calorimeter (ECAL) consisting of 1596 lead tungstate PbWO 4 scintillating crystals has been fabricated and installed in the experimental Hall D at Jefferson Lab (JLab). The highgranularity, high-resolution calorimeter is required by the JLab Eta Factory experiment, whose main physics goal is to study rare decays of eta mesons. The ECAL replaced the inner part of the forward lead glass calorimeter of the GlueX detector. Signals from the detector will be digitized using twelve-bit flash analog-to-digital converters operated at a sampling rate of 250 MHz. The ECAL is integrated into the trigger system of the GlueX detector using electronics modules designed at JLab. The ECAL is currently at the commissioning stage and should be ready for the physics run in January 2025. We will give an overview of the JEF experiment, the design and construction of the ECAL, and the integration of the detector and its infrastructure into the Hall D experimental setup.

Somov, Alexander [Thomas Jefferson National Accele↗
DOE OSTI2011

B-Meson and Neutrino Oscillation: A Unified Treatment

We present a unified treatment of the quantum mechanics of B-factory and neutrino oscillation experiments. While our approach obtains the usual phenomenological predictions for these experiments, it does so without having to invoke perplexing Einstein-Podolsky-Rosen correlations or non-intuitive kinematical assumptions. The quantum mechanics of mixing during propagation is at the heart of both B-factory and neutrino oscillation experiments. In this paper, we will treat both these experiments in the same way. Our treatment has several advantages. In dealing with the B-factory experiments, it avoids having to invoke real but nonetheless puzzling Einstein-Podolsky-Rosen correlations. In dealing with neutrino oscillation, our approach avoids the non-intuitive assumption that all the interfering neutrino mass eigenstates in a beam have the same energy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Review of Heavy Flavor Physics at the Tevatron

The D0 and CDF detectors at the Fermilab Tevatron have each accumulated more that 9 fb{sup -1} of integrated luminosity. The corresponding large datasets enable the two experiments to perform unprecedented studies of heavy flavor hadron properties. We present recent D0 and CDF measurements, focusing on rare decays and CP violation in B-meson decays. Flavor Physics probes new phenomena by either searching for small deviations from the Standard Model (SM) based theoretical predictions or by measuring quantities which are highly suppressed within the SM. Searching for small deviations from the SM are performed using large strange, charm or bottom hadron samples, mostly by kaon experiments of B factories. Measurements of highly suppressed quantities, such as CP violation phases and asymmetries in the neutral B{sub s}-meson system or searches for rare B decays, are performed with the hope that new physics effects would be large enough to significantly affect the measured quantities and so, lead to observations of deviations from the SM expectations. The D0 and CDF detectors at the Fermilab Tevatron have each accumulated more that 9 fb{sup -1} of integrated luminosity. The corresponding large datasets enable the two experiments to perform unprecedented studies of heavy flavor hadron properties. We present recent D0 and CDF measurements, focusing on rare decays and CP violation in B-meson decays.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

A supersymmetric theory of baryogenesis and sterile sneutrino dark matter from B mesons

Low-scale baryogenesis and dark matter generation can occur via the production of neutral B mesons at MeV temperatures in the early Universe, which undergo CP-violating oscillations and subsequently decay into a dark sector. In this work, we discuss the consequences of realizing this mechanism in a supersymmetric model with an unbroken U(1) R symmetry which is identified with baryon number. B mesons decay into a dark sector through a baryon number conserving operator mediated by TeV scale squarks and a GeV scale Dirac bino. The dark sector particles can be identified with sterile neutrinos and their superpartners in a type-I seesaw framework for neutrino masses. The sterile sneutrinos are sufficiently long lived and constitute the dark matter. The produced matter-antimatter asymmetry is directly related to observables measurable at B factories and hadron colliders, the most relevant of which are the semileptonic-leptonic asymmetries in neutral B meson systems and the inclusive branching fraction of B mesons into hadrons and missing energy. We discuss model independent constraints on these experimental observables before quoting predictions made in the supersymmetric context. Constraints from astrophysics, neutrino physics and flavor observables are studied, as are potential LHC signals with a focus on novel long lived particle searches which are directly linked to properties of the dark sector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

CKM-UT Angles: Mixing And CP Violation at the B Factories

We review the experimental status of the angles of the Unitarity Triangle of the CKM matrix, as measured by the BABAR and Belle experiments. The B Factories have demonstrated since the beginning of this decade that CP violation in the B meson system is consistent with the Standard Model (SM) description in terms of the complex phase in the three-by-three Cabibbo-Kobayashi-Maskawa (CKM) matrix. With one single phase, the SM predicts clear patterns for quark mixing and CP violations, to be satisfied by all processes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Observation of B ¯ → D ( * ) π + π - ℓ - ν ¯ Decays in e + e - Collisions at the Υ ( 4 S ) Resonance

We report on measurements of the decays of $\bar{B}$ mesons into the semileptonic final states $\bar{B}$→D(*)π + π - l - $\bar{v}$, where D(*) represents a D or D* meson and l - is an electron or a muon. These measurements are based on 471×10 6 B$\bar{B}$ pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R$(*)\atop{π+π-}$ = B($\bar{B}$→D(*)π + π - l - $\bar{v}$)/B($\bar{B}$→D(*)l - $\bar{v}$) using events in which the second B meson is fully reconstructed. We find R π+π- =0.067 ± 0.010 ± 0.008 and R$*\atop{π+π-}$ = 0.019 ± 0.005 ± 0.004, where the first uncertainty is statistical and the second is systematic. Lastly, based on these results and assuming isospin invariance, we estimate that $\bar{B}$→D(*)ππl - $\bar{v}$ decays, where π denotes either a π ± and π 0 meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Future Physics Programme of BESIII

There has recently been a dramatic renewal of interest in hadron spectroscopy and charm physics. This renaissance has been driven in part by the discovery of a plethora of charmonium-like XYZ states at BESIII and B factories, and the observation of an intriguing proton-antiproton threshold enhancement and the possibly related X(1835) meson state at BESIII, as well as the threshold measurements of charm mesons and charm baryons. We present a detailed survey of the important topics in tau-charm physics and hadron physics that can be further explored at BESIII during the remaining operation period of BEPCII. This survey will help in the optimization of the data-taking plan over the coming years, and provides physics motivation for the possible upgrade of BEPCII to higher luminosity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Status of the JLab Eta Factory (JEF) experiment

The JLab Eta Factory (JEF) experiment is an approved experiment in Hall D at Jefferson Lab that focuses on decays of ? mesons produced in the reaction ?p?p? with emphasis on the rare ???0?? channel. In addition to providing a rare window into higher-order chiral perturbation theory, this channel can be used to search for evidence of dark matter. A potential extension to the Standard Model posits a dark gauge boson B that couples predominately with quarks and can be observed in the ???B, B??0? channel\footnote{S.~Tulin, Phys.\ Rev.\ D {\bf 89}, no. 11, 114008 (2014).}. The same set of final state particles can also be used to look for a scalar dark matter mediator S in the ???0S, S??? channel\footnote{B.~Batell, A.~Freitas, A.~Ismail and D.~McKeen, arXiv:1812.05103 [hep-ph].}. In order to achieve the requisite resolution to clearly identify these rare channels, this experiment calls for an upgrade to the existing GlueX equipment, which is a fixed target apparatus based on a 2-Tesla solenoid magnet (which enables reconstruction of the momentum of the recoil proton). Neutral particles emerging after the interaction of the photon beam with a liquid hydrogen target are detected in the forward direction in the Forward Calorimeter (FCAL), an array of lead glass blocks. We plan to replace the ?80×80 cm2 region of the FCAL closest to the beam line with an array of 2×2×20 cm3 lead tungstate crystals. The current status of the JEF project will be presented.

Taylor, Simon↗
DOE OSTI2011

Searches for Leptonic B Decays at BaBar

The authors present the most recent results on the leptonic B decays B {yields} lv, B {yields} lv{gamma}, based on the data collected by the BABAR experiment at PEP-II, an asymmetric e{sup +}e{sup -} collider at the center of mass energy of the {Upsilon}(4S) resonance. Leptonic B decays are an excellent probe for new Physics, branching fraction measurements being complementary to the direct searches at high energy machines. Current experimental measurements are in agreement with Standard Model expectations, but, being already capable to constrain parameters of New Physics models today, they will be golden channels for the foreseen super flavor factories.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

D0 - D0bar Mixing: An Overview

Recently, the B factory experiments BABAR and Belle as well as the CDF collaboration found evidence for mixing in the D meson system. The current status (beginning of summer 2008) of the experimental results of D{sup 0} mixing is summarized. In this paper, we present an overview of D{sup 0} mixing. After an introduction to the charm mixing phenomenology and analysis techniques, results of the mixing parameters and CP violation as related to mixing are summarized. They are obtained from hadronic two-body, multi-body final states and from quantum correlated D{sup 0} decays of the experiments BABAR, Belle, Cleo and CDF. Mixing results from semileptonic D{sup 0} decays can be found elsewhere.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

New States and Charmonium Spectroscopy at BaBar

Several charmonium-like states above D{bar D} threshold have been discovered at the Belle and BaBar B-factories. Some are produced via Initial State Radiation (e.g. Y(4260) and Y(4350)), and some are observed in B meson decays (e.g. X(3872), Y(3940), and Z-(4430)). The Z-(4430) state has generated a great deal of interest, having minimum quark content (c{bar c}d{bar u}) and, thus, representing the unequivocal manifestation of a four-quark meson state. Here we summarize recent BaBar results on the Y(4260), X(3872), Y(3940), and on a search for the Z-(4430).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗