1,687 research outputs found
Measurement of bar{B0} Meson Properties Via Partial Reconstruction of the Decay bar{B0} -> D*+ l- ar{nu}
No full textUsing data recorded by the CLEO II detector operating at the Upsilon(4S) resonance at the Cornell Electron Storage Ring, several properties of B mesons are measured using a partially reconstructed tag of the decay mode bar{B0} -> D*+ l- bar{nu}. Using 2.38 fb**{-1} of on-resonance data and the averaged B meson semileptonic branching fraction through inclusive lepton momentum spectrum obtained by previous CLEO analysis, we measure the B0 and B- semileptonic branching fraction to be (10.78 +/- 0.60 +/- 0.69)% and (10.25 +/- 0.57 +/- 0.65)% respectively, which yields the lifetime ratio tau_+/tau_0 = 0.950 +0.117-0.080 +0.091-0.068, assuming the equality of semileptonic partial branching width for bar{B0} and B-. With a larger dataset of 3.1 fb**{-1}, we measured the B0-bar{B0} mixing parameter chi_d to be 0.189 +/- 0.019 +/- 0.006.Ph. D
Search the decay of the B meson to two leptons at the Belle Experiment
No full textThe set of decays known as B⁰ → l⁺l⁻ are exceedingly rare. This thesis details procedures developed to optimize signal extraction and improve the upper limit on the measured branching fraction. When applied to 85 million BB events collected at the Belle experiment in Tsukuba, Japan, the resulting upper limits on branching fractions were 8.8×10⁻⁸ for B⁰ → e⁺e⁻, 1.0×10⁻⁷ for B⁰ → μ⁺μ⁻, and 8.5×10⁻⁸ for B⁰ → e±μ∓" at the 90% confidence level.Ph. D
Properties of LEDs for the Calibration of PMTs for the Daya Bay Project
No full textThe flavor oscillations of neutrinos due to the mixing of mass eigenstates have been thoroughly studied in several experiments. One missing piece of the puzzle is the mixing angle θ13, which is being searched for by the Daya Bay experiment. Currently, the experiment is still in construction mode. Part of the experiment involves building effective detectors for atmospheric muons, resulting in accurate detection of antineutrinos from the source. To ensure accurate detection, we must effectively calibrate the PMTs with the use of carefully chosen and calibrated LEDs. This thesis details the study of several LEDs measured in an attempt to determine the properties of the most likely source for our calibration efforts. I measured the spectra of the LEDs meant for use in calibration, along with several others for the purpose of comparison of spectrum width and to find the evidence of fluorescence in the LEDs.Master of Scienc
Bottomonium Spectroscopy at Belle: Studies of Radiative and Hadronic Transitions
No full textThe large constituent quark mass of bottomonium, the bottom quark/anti-quark bound state , affords a rich spectroscopy in which the perturbative (non-relativistic) limit of Quantum Chromodynamics may be theoretically described and experimentally investigated. The radial excitations of bottomonia---with radial quantum number , one unit of total angular momentum , and orbital angular momentum , labeled ---are copiously produced in electron--positron collisions.
The Belle Collaboration is a high energy physics experiment located at the KEKB B-Factory epem collider, based at KEK in Tsukuba, Japan. Belle has accumulated a large dataset near the FourS and ThreeS resonances, collectively containing more than 28 million ThreeS and 556 million FourS. Some of these decay to other bbbar states---with one unit of orbital angular momentum and total angular momentum , labeled cbj{n} ---via the emission of a photon, with subsequent transition to the OneS with the emission of one or more gluons, which hadronize to form an om meson.
This dissertation presents an analysis of the hadronic transitions , where with , at Belle. The transitions of the triplet states provide a unique laboratory in which to study nonrelativistic quantum chromodynamics (NRQCD), as the kinematic threshold for production of an and lies between the and states. The results presented herein constitute the first confirmation measurement of the transitions of the states since their discovery in 2004, with evidence---in excess of three standard deviations---for the sub-threshold transition of the state. The branching fraction is found to be as large as the corresponding rate for the transition. The ratio of the to transitions is also measured and compared with the expectation from NRQCD, which we compute, revealing a tension between experiment and theory. This work is leveraged to perform a search for radiative transitions of the to the and states, which are reconstructed in an inclusive final state. With no significant signal seen, limits are set on the corresponding branching fractions.Doctor of PhilosophyAtoms, the stuff of everyday matter, consist of a number of electrons bound to a compact nucleus. This nucleus, in turn, contains one or more protons and neutrons, which are themselves made up of constituent particles called quarks that interact with one another by exchanging particles called gluons. Although great strides were made during the last century to further our understanding of the fundamental structure of matter, a comprehensive description of nuclear structure, at the quark level, eludes us. What we do know is that the force responsible for binding the large number of positively charged protons within the narrowly confined nucleus of, say, a gold atom is incredibly strong---in reality, more than 137 times as strong as the electromagnetic (EM) interaction, which is responsible for binding electrons around the nucleus in atoms. Unlike the EM force, which has one charge that can be either positive or negative, the strong interaction has three. This leads to a manifestly more complicated phenomena whose mathematical descriptions are computationally intractable.
To study the strong interaction, we seek out the simplest of strongly bound states---called the meson---which consist of a quark and its anti-particle counterpart. The meson made up of a bottom quark/anti-quark pair, called bottomonium, provides an ideal laboratory for our investigations. In bottomonium, the quarks are very heavy (about 4.5 times the mass of a proton) and move relatively slowly compared to the quarks within a proton. This allows for some simplifications in the mathematical description of the bottomonium system, making it possible to compute predictions that can be tested in the lab. In this low energy regime, the strong interaction gives rise to a family of excited bottomonium states that have a structure similar to the excited states of an atom. Just as scientists learned about the EM interaction by studying the decays of excited atomic states, so too do we study the strong force by measuring the decays of bottomonium states. We call this study heavy quarkonium spectroscopy. When excited bottomonium states transition to lower-energy states, they may emit photons (as excited atoms do) or gluons. These emitted gluons, in turn, produce other particles. Measurements of the decay rates of bottomonium states may be predicted from the mathematical description of the strong interaction, providing direct experimental tests of the theoretical models. This dissertation presents a study of the decays of several bottomonium states, which are produced at the Belle experiment at the KEKB electron--positron collider. The decay rates, called the branching fractions, of these transitions are measured and used to test the prediction from theory, which we calculate. This work is leveraged to search for several previously unobserved decays, which are expected to be exceptionally rare
First observation of B → D ̄_1 (→ D ̄ π+π-) l+ν l and measurement of the B → D ̄(∗) π l+ νl and B → D ̄(∗) π+ π- l+ νl branching fractions with hadronic tagging at Belle
No full textWe report measurements of the ratios of branching fractions for B→D ̄(∗)πl+νl and B→D ̄(∗)π+π-l+νl relative to B→D ̄∗l+νl decays with l=e, μ. These results are obtained from a data sample that contains 772×106BB ̄ pairs collected near the Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. Fully reconstructing both B mesons in the event, we obtain B(B0→D ̄0π-l+νl)B(B0→D∗-l+νl)=(7.23±0.36±0.14)%, B(B+→D-π+l+νl)B(B+→D ̄∗0l+νl)=(6.78±0.24±0.18)%, B(B0→D ̄∗0π-l+νl)B(B0→D∗-l+νl)=(11.10±0.48±0.23)%, B(B+→D∗-π+l+νl)B(B+→D ̄∗0l+νl)=(9.50±0.33±0.34)%, B(B0→D-π+π-l+νl)B(B0→D∗-l+νl)=(2.91±0.37±0.26)%, B(B+→D ̄0π+π-l+νl)B(B+→D ̄∗0l+νl)=(3.10±0.26±0.22)%, B(B0→D∗-π+π-l+νl)B(B0→D∗-l+νl)=(0.99±0.43±0.20)%, B(B+→D ̄∗0π+π-l+νl)B(B+→D ̄∗0l+νl)=(1.25±0.27±0.15)%, where the uncertainties are statistical and systematic, respectively. These are the most precise measurements of these branching fraction ratios to date. The invariant mass spectra of the Dπ, D∗π, and Dππ systems are studied, and the branching fraction products B(B0→D2∗-l+νl)×B(D2∗-→D ̄0π-)=(0.157±0.015±0.005)%, B(B+→D ̄0∗0l+νl)×B(D ̄0∗0→D-π+)=(0.054±0.022±0.005)%, B(B+→D ̄2∗0l+νl)×B(D ̄2∗0→D-π+)=(0.163±0.011±0.008)%, B(B0→D1-l+νl)×B(D1-→D ̄∗0π-)=(0.306±0.050±0.029)%, B(B0→D1′-l+νl)×B(D1′-→D ̄∗0π-)=(0.206±0.068±0.025)%, B(B0→D2∗-l+νl)×B(D2∗-→D ̄∗0π-)=(0.051±0.040±0.010)%, B(B+→D ̄10l+νl)×B(D ̄10→D∗-π+)=(0.249±0.023±0.015)%, B(B+→D ̄1′0l+νl)×B(D ̄1′0→D∗-π+)=(0.138±0.036±0.009)%, B(B+→D ̄2∗0l+νl)×B(D ̄2∗0→D∗-π+)=(0.137±0.026±0.009)%, B(B0→D1-l+νl)×B(D1-→D-π+π-)=(0.102±0.013±0.009)%, B(B+→D ̄10l+νl)×B(D ̄10→D ̄0π+π-)=(0.105±0.011±0.009)%, are extracted. This is the first observation of the decays B→D ̄1l+νl with D1→Dπ+π-
Search for the lepton-flavor-violating τ− → e∓l±l− decays at Belle II
No full textWe present the result of a search for the charged-lepton-flavor violating decays τ− → e∓l±l−, where l is a muon or an electron, using a data sample with an integrated luminosity of 428 fb−1 recorded by the Belle II experiment at the SuperKEKB e+e− collider. The selection of e+e− → τ+τ− events containing a signal candidate is based on an inclusive-tagging reconstruction and on a boosted decision tree to suppress background. Upper limits on the branching fractions between 1.3 and 2.5 × 10−8 are set at the 90% confidence level. These results are the most stringent bounds to date for four of the modes
Science and Technology of a Low-Energy Solar Neutrino Spectrometer (LENS) and Development of the MiniLENS Underground Prototype
No full textA real time low energy spectral measurement of the neutrinos coming from the Sun will give us a greater understanding of energy production in the Sun, and the mechanisms of neutrino mixing. We will, for the first time, measure the solar neutrino spectrum for all solar neutrinos <2MeV in particular pp, Be and CNO neutrinos, be able to compare the solar photon derived energy luminosity (Lï §) to the solar neutrino derived energy luminosity (Lï ®) independent of any solar model, explore dark energy with respect to mass varying neutrinos, and explore CNO abundances in the Sun. These measurements require new technology in Indium loaded scintillators and large scale detector designs, namely increased spatial resolution through a novel scintillation lattice. I will present the advances we are making to these fields at Virginia Tech as well as neutrino science and the physics of the LENS detector.Ph. D
- …
