117089413
Power tests of the Fermilab Lithium Lens for antiproton collection
A prototpye Lithium Lens to be used for the collection of antiprotons in the Fermilab Tevatron I project has been constructed. Some of the fabrication details, the procedure for lithium filling and the results of the initial operation are discussed.
46560389
Helium Refrigeration System and Cryogenic System for Superconducting Switchyard Magnets at Fermilab
The first Fermilab Satellite Refrigerator produced from commercially built components has been operated in the Switchyard in a stand alone mode. After some initial shakedown runs, it has been used to cool two magnetically opposed superconducting magnets in the external beam line to the Meson Laboratory. This equipment was installed as a test of the cryogenic system to be used in converting the entire major horizontal bend to superconducting magnets (currently containing 56 conventional 10 foot dipoles). We report here on the successful operation of the refrigerator, our operating experience with the cryo nic system, and the successful transport of 1.8 x 10'1 350 GeV protons per pulse through the magnets. The complete system was designed and built by Fermilab personnel. Process and component specification and design were shared by Fermilab and an independent consulting firm.1
117708238
STACKTAIL MOMENTUM COOLING IN THE FERMILAB ANTIPROTON SOURCE
45030934
Superconducting Delay Line for Stochastic Cooling Filters
The stochastic cooling system of the antiproton source at Fermilab uses notch filters for reducing the feedback power at frequencies corresponding to particles in the core. At the same time these filters assist in shaping the gain vs. momentum in the stack tail. These filters, therefore, must attenuate all the harmonics of the revolution frequency (629 kHz) in the operating frequency band (1-2 GHz). They require components providing delays of 1.59 microseconds with a minimum of attenuation and undesirable distortion in this passband. Transmission lines providing such delays are typically 328 m long, have a rather large diameter, and are fabricated from a high conductivity material to keep the attenuation sufficiently low. The use of superconductors allows a dramatic reduction in the diameter, total size, and cost of this component in spite of the added cryogenic requirements. The authors measured the performance of two such cables in order to demonstrate the feasibility of the superconducting cable-notch filter concept. The first cable is an 84 m long superconducting coax consisting of a solid Niobium inner conductor inside a teflon dielectric, a lead outer conductor, and an outer jacket of mylar tape. The second cable is a 1.0 km long coaxial line more » with an inner conductor of lead-plated copper wire, a FEP teflon dielectric, and an outer conductor of leadplated copper tape wrapped with mylar. This paper discusses the results of performance testing of both cables and assesses their compatibilities with notch filters. « less
55383487
Operational Experience with Tevatron I Antiproton Source
The secondaries are transported down the AP2 line into the Debuncher ring. The Debdncher ring has a 207 x 23~ transverse acceptance and 4% momentum acceptance. The antiprotons are then rotated using 4.2 MV of 53 MHz R.F. to .4% Ap/p in 80 turns and the adIabatically debunched to .2% APIP. The antiproton are then stochastically cooled for 2 seconds in the transverse planes with 2-4 GHz cooling systems to 771 x 77. The antiproton are then extracted from the Debuncher and transported across the D/A line to the Accumulator.
121309706
Measurements of magnet quench levels induced by proton beam spray
A superconducting dipole magnet was installed in the Fermilab primary beam line. Targets were inserted in the proton beam upstream of the magnet and measurements made of the energy deposition within the magnet sufficient to cause quenching. The quench levels were 25 mW/g for 1 sec beam spill and 1 mJ/g for a spill of 1 msec or less. In comparison, the energy deposition at the extraction septum was 0.6 mJ/g.
119217152
Observation of $B^+_c \rightarrow J/\psi D_s^+$ and $B^+_c \rightarrow J/\psi D_s^{*+}$ decays
The decays $B^+_c \rightarrow J/\psi D_s^+$ and $B^+_c \rightarrow J/\psi D_s^{*+}$ are observed for the first time using a dataset, corresponding to an integrated luminosity of 3$fb^{-1}$, collected by the LHCb experiment in proton-proton collisions at centre-of-mass energies of $\sqrt{s}$=7 and 8 TeV. The statistical significance for both signals is in excess of 9 standard deviations. The following ratios of branching fractions are measured to be $BR(B^+_c \rightarrow J/\psi D_s^+)/BR(B^+_c \rightarrow J/\psi \pi+) = 2.90 \pm 0.57 \pm 0.24$, $BR(B^+_c \rightarrow J/\psi D_s^{*+}) / BR (B^+_c \rightarrow J/\psi D_s^+) = 2.37 \pm 0.56 \pm 0.10$, where the first uncertainties are statistical and the second systematic. The mass of the \Bc meson is measured to be $m_{B^+_c} = 6276.28 \pm 1.44 (stat) \pm 0.36(syst) MeV/c^2$, using the $B^+_c \rightarrow J/\psi D_s^+$ decay mode.
32493630
Computer Modeling of Internal Targets in Electron Storage Rings
The effect of thin (1-50 ¿gm/cm2) internal targets on beam quality in electron storage rings is evaluated. The internal target is modeled assuming that scattering is the result of elastic collisions between the beam electrons and the target nuclei. A screened coulomb potential is used and single and plural scattering mechanisms are included. A storage ring particle tracking code, DIMAT, was modified to include the internal target model and used to obtain the results discussed. Beam particle loss distributions and beam envelope "growth times" are given and discussed in light of damping mechanisms inherent in electron storage ring designs.
116943240
Measurement of the semileptonic $CP$ asymmetry in $B^0-\overline{B}{}^0$ mixing
The semileptonic $CP$ asymmetry in $B^0-\overline{B}{}^0$ mixing, $a_{\rm sl}^d$, is measured in proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb$^{-1}$, recorded by the LHCb experiment. Semileptonic $B^0$ decays are reconstructed in the inclusive final states $D^-\mu^+$ and $D^{*-}\mu^+$, where the $D^-$ meson decays into the $K^+\pi^-\pi^-$ final state, and the $D^{*-}$ meson into the $\overline{D}{}^0(\rightarrow K^+\pi^-)\pi^-$ final state. The asymmetry between the numbers of $D^{(*)-}\mu^+$ and $D^{(*)+}\mu^-$ decays is measured as a function of the decay time of the $B^0$ mesons. The $CP$ asymmetry is measured to be $a_{\rm sl}^d = (-0.02 \pm 0.19 \pm 0.30)\%$, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of $a_{\rm sl}^d$ to date and is consistent with the prediction from the Standard Model.
17341590
A study of lithium deuteride as a material for a polarized target
Abstract Experiment E155 at the Stanford Linear Accelerator Center (SLAC) measured the spin-dependent structure of the proton and neutron, using for the first time 6 LiD as the polarized deuteron target material in a high-energy electron beam. This compound provides a significantly higher dilution factor than any other solid deuteron target material currently used in high-energy physics experiments. Results of the polarization behavior of the 6 LiD target material before and after exposure to the 50 GeV/ c electron beam used in E155 are presented.
197530514
Observation of a resonance in $B^+ \to K^+ \mu^+\mu^-$ decays at low recoil
A broad peaking structure is observed in the dimuon spectrum of $B^+ \to K^+ \mu^+\mu^-$ decays in the kinematic region where the kaon has a low recoil against the dimuon system. The structure is consistent with interference between the $B^+ \to K^+ \mu^+\mu^-$ decay and a resonance and has a statistical significance exceeding six standard deviations. The mean and width of the resonance are measured to be $4191^{+9}_{-8}\mathrm{\,Me\kern -0.1em V/}c^2$ and $65^{+22}_{-16}\mathrm{\,Me\kern -0.1em V/}c^2$, respectively, where the uncertainties include statistical and systematic contributions. These measurements are compatible with the properties of the $\psi(4160)$ meson. First observations of both the decay $B^+ \to \psi(4160) K^+$ and the subsequent decay $\psi(4160) \to \mu^+\mu^-$ are reported. The resonant decay and the interference contribution make up 20\,% of the yield in the low recoil region, which is larger than theoretical estimates.