arXiv subjects

R. Godang

Publications and source records attributed to R. Godang.

At least 19 recordsLinked to original sources

arXiv2024

The Belle II Detector Upgrades Framework Conceptual Design Report

We describe the planned near-term and potential longer-term upgrades of the Belle II detector at the SuperKEKB electron-positron collider operating at the KEK laboratory in Tsukuba, Japan. These upgrades will allow increasingly sensitive searches for possible new physics beyond the Standard Model in flavor, tau, electroweak and dark sector physics that are both complementary to and competitive with the LHC and other experiments.

hep-ex↗

arXiv2022

Snowmass 2021 White Paper on Upgrading SuperKEKB with a Polarized Electron Beam: Discovery Potential and Proposed Implementation

Upgrading the SuperKEKB electron-positron collider with polarized electron beams opens a new program of precision physics at a center-of-mass energy of 10.58 GeV. This white paper describes the physics potential of this `Chiral Belle' program. It includes projections for precision measurements of $\sin^2\theta_W$ that can be obtained from independent left-right asymmetry measurements of $e^+e^-$ transitions to pairs of electrons, muons, taus, charm and b-quarks. The $\sin^2\theta_W$ precision obtainable at SuperKEKB will match that of the LEP/SLC world average, but at the centre-of-mass energy of 10.58 GeV. Measurements of the couplings for muons, charm, and $b$-quarks will be substantially improved and the existing $3\sigma$ discrepancy between the SLC $A_{LR}$ and LEP $A_{FB}^b$ measurements will be addressed. Precision measurements of neutral current universality will be more than an order of magnitude more precise than currently available. As the energy scale is well away from the $Z^0$-pole, the precision measurements will have sensitivity to the presence of a parity-violating dark sector gauge boson, $Z_{\rm dark}$. The program also enables the measurement of the anomalous magnetic moment $g-2$ form factor of the $\tau$ to be made at an unprecedented level of precision. A precision of $10^{-5}$ level is accessible with 40~ab$^{-1}$ and with more data it would start to approach the $10^{-6}$ level. This technique would provide the most precise information from the third generation about potential new physics explanations of the muon $g-2$ $4\sigma$ anomaly. Additional $\tau$ and QCD physics programs enabled or enhanced with having polarized electron beams are also discussed in this White Paper. This paper includes a summary of the path forward in R&D and next steps required to implement this upgrade and access its exciting discovery potential.

physics.acc-ph↗

arXiv2022

Belle II Executive Summary

Belle II is a Super $B$ Factory experiment, expected to record 50 ab$^{-1}$ of $e^+e^-$ collisions at the SuperKEKB accelerator until 2035. The large samples of $B$ mesons, charm hadrons, and tau leptons produced in the clean experimental environment of $e^+e^-$ collisions will provide the basis of a broad and unique flavor-physics program. Belle II will pursue physics beyond the Standard Model in many ways, for example: improving the precision of weak interaction parameters, particularly Cabibbo-Kobayashi-Maskawa (CKM) matrix elements and phases, and thus more rigorously test the CKM paradigm, measuring lepton-flavor-violating parameters, and performing unique searches for missing-mass dark matter events. Many key measurements will be made with world-leading precision.

hep-ex↗

arXiv2021

$B$-flavor tagging at Belle II

We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom ($B$) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic $B$ decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of $62.8$ fb$^{-1}$, collected at the $\Upsilon$(4$S$) resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be $\varepsilon_{\rm eff} = \big(30.0 \pm 1.2(\text{stat}) \pm 0.4(\text{syst})\big)\%$ for a category-based algorithm and $\varepsilon_{\rm eff} = \big(28.8 \pm 1.2(\text{stat}) \pm 0.4(\text{syst})\big)\%$ for a deep-learning-based algorithm.

hep-ex↗

arXiv2020

Search for Axion-Like Particles produced in $e^+e^-$ collisions at Belle II

We present a search for the direct production of a light pseudoscalar $a$ decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process ${e^+e^-\to\gamma a, a \to\gamma\gamma}$ in the mass range ${0.2} \,< m_a < {9.7}\,{\text{GeV/$c$}^2}$ using data corresponding to an integrated luminosity of $(445\pm 3)\,\text{pb}^{-1}$. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axion-like particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength $g_{a\gamma\gamma}$ of ALPs to photons at the level of $10^{-3}\,{\text{GeV}^{-1}}$. The limits are the most restrictive to date for $0.2\,<\,m_a\,<\,1\,{\text{GeV/$c$}^2}$.

hep-ex↗

arXiv2020

Search for an invisibly decaying $Z^{\prime}$ boson at Belle II in $e^+ e^- \to μ^+ μ^- (e^{\pm} μ^{\mp})$ plus missing energy final states

Theories beyond the standard model often predict the existence of an additional neutral boson, the $Z^{\prime}$. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a $Z^{\prime}$ in the process $e^+ e^- \to μ^+ μ^- Z^{\prime}$ and of a lepton-flavor-violating $Z^{\prime}$ in $e^+ e^- \to e^{\pm} μ^{\mp} Z^{\prime}$. We do not find any excess of events and set 90\% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an $L_μ-L_τ$ theory, into upper limits on the $Z^{\prime}$ coupling constant at the level of $5 \times 10^{-2}$ -- $1$ $M_{Z^\prime}\leq 6$ GeV/$c^2$.

hep-ex↗

arXiv2009

Averages of b-hadron and c-hadron Properties at the End of 2007

This article reports world averages for measurements of b-hadron and c-hadron properties obtained by the Heavy Flavor Averaging Group (HFAG) using the results available at the end of 2007. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, and parameters of semileptonic decays.

hep-ex↗

arXiv2007

Catfish: A Monte Carlo simulator for black holes at the LHC

We present a new Fortran Monte Carlo generator to simulate black hole events at CERN's Large Hadron Collider. The generator interfaces to the PYTHIA Monte Carlo fragmentation code. The physics of the BH generator includes, but not limited to, inelasticity effects, exact field emissivities, corrections to semiclassical black hole evaporation and gravitational energy loss at formation. These features are essential to realistically reconstruct the detector response and test different models of black hole formation and decay at the LHC.

hep-ph↗

arXiv2007

Muon Acceleration to 750 GeV in the Tevatron Tunnel for a 1.5 TeV mu+ mu- Collider

Muon acceleration from 30 to 750 GeV in 72 orbits using two rings in the 1000m radius Tevatron tunnel is explored. The first ring ramps at 400 Hz and accelerates muons from 30 to 400 GeV in 28 orbits using 14 GV of 1.3 GHz superconducting RF. The ring duplicates the Fermilab 400 GeV main ring FODO lattice, which had a 61m cell length. Muon survival is 80%. The second ring accelerates muons from 400 to 750 GeV in 44 orbits using 8 GV of 1.3 GHz superconducting RF. The 30 T/m main ring quadrupoles are lengthened 87% to 3.3m. The four main ring dipoles in each half cell are replaced by three dipoles which ramp at 550 Hz from -1.8T to +1.8T interleaved with two 8T fixed superconducting dipoles. The ramping and superconducting dipoles oppose each other at 400 GeV and act in unison at 750 GeV. Muon survival is 92%. Two mm copper wire, 0.28mm grain oriented silicon steel laminations, and a low duty cycle mitigate eddy current losses. Low emittance muon bunches allow small aperatures and permit magnets to ramp with a few thousand volts. Little civil construction is required. The tunnel exists.

physics.acc-ph↗

arXiv2006

Averages of b-hadron Properties at the End of 2005

This article reports world averages for measurements on b-hadron properties obtained by the Heavy Flavor Averaging Group (HFAG) using the available results as of at the end of 2005. In the averaging, the input parameters used in the various analyses are adjusted (rescaled) to common values, and all known correlations are taken into account. The averages include lifetimes, neutral meson mixing parameters, parameters of semileptonic decays, branching fractions of B meson decays to final states with open charm, charmonium and no charm, and measurements related to CP asymmetries.

hep-ex↗

arXiv2005

6D Muon Ionization Cooling with an Inverse Cyclotron

A large admittance sector cyclotron filled with LiH wedges surrounded by helium or hydrogen gas is explored. Muons are cooled as they spiral adiabatically into a central swarm. As momentum approaches zero, the momentum spread also approaches zero. Long bunch trains coalesce. Energy loss is used to inject the muons into the outer rim of the cyclotron. The density of material in the cyclotron decreases adiabatically with radius. The sector cyclotron magnetic fields are transformed into an azimuthally symmetric magnetic bottle in the center. Helium gas is used to inhibit muonium formation by positive muons. Deuterium gas is used to allow captured negative muons to escape via the muon catalyzed fusion process. The presence of ionized gas in the center may automatically neutralize space charge. When a bunch train has coalesced into a central swarm, it is ejected axially with an electric kicker pulse.

physics.acc-ph↗

arXiv2005

The RFOFO Ionization Cooling Ring for Muons

Practical ionization cooling rings could lead to lower cost or improved performance in neutrino factory or muon collider designs. The ring modeled here uses realistic three-dimensional fields. The performance of the ring compares favorably with the linear cooling channel used in the second US Neutrino Factory Study. The normalized 6D emittance of an ideal ring is decreased by a factor of approximately 240, compared with a factor of only 15 for the linear channel. We also examine such \textit{real-world} effects as windows on the absorbers and rf cavities and leaving empty lattice cells for injection and extraction. For realistic conditions the ring decreases the normalized 6D emittance by a factor of 49.

physics.acc-ph↗

arXiv2005

6D Ionization Muon Cooling with Tabletop Rings

Progress on six dimensional ionization muon cooling with relatively small rings of magnets is described. Lattices being explored include scaling sector cyclotrons with edge focusing and strong focusing, fixed field alternating gradient (FFAG) rings. Ionization cooling is provided by high pressure hydrogen gas which removes both transverse and longitudinal momentum. Lost longitudinal momentum is replaced using radio frequency (RF) cavities, giving a net transverse emittance reduction. The longer path length in the hydrogen of higher momentum muons decreases longitudinal emittance at the expense of transverse emittance. Thus emittance exchange allows these rings to cool in all six dimensions and not just transversely. Alternatively, if the RF is located after the ring, it may be possible to cool the muons by stopping them as they spiral adiabatically into a central swarm. As momentum goes to zero, the momentum spread goes to zero. The resulting cooled muons can lead to an intense muon beam which could be a source for neutrino factories or muon colliders.

physics.acc-ph↗

arXiv2004

Multi-Terabyte EIDE Disk Arrays running Linux RAID5

High-energy physics experiments are currently recording large amounts of data and in a few years will be recording prodigious quantities of data. New methods must be developed to handle this data and make analysis at universities possible. Grid Computing is one method; however, the data must be cached at the various Grid nodes. We examine some storage techniques that exploit recent developments in commodity hardware. Disk arrays using RAID level 5 (RAID-5) include both parity and striping. The striping improves access speed. The parity protects data in the event of a single disk failure, but not in the case of multiple disk failures. We report on tests of dual-processor Linux Software RAID-5 arrays and Hardware RAID-5 arrays using a 12-disk 3ware controller, in conjunction with 250 and 300 GB disks, for use in offline high-energy physics data analysis. The price of IDE disks is now less than $1/GB. These RAID-5 disk arrays can be scaled to sizes affordable to small institutions and used when fast random access at low cost is important.

physics.data-an↗

arXiv2004

Resolution of Nearly Mass Degenerate Higgs Bosons and Production of Black Hole Systems of Known Mass at a Muon Collider

The direct s-channel coupling to Higgs bosons is 40000 times greater for muons than electrons; the coupling goes as mass squared. High precision scanning of the lighter $h^0$ and the higher mass $H^0$ and $A^0$ is thus possible with a muon collider. The $H^0$ and $A^0$ are expected to be nearly mass degenerate and to be CP even and odd, respectively. A muon collider could resolve the mass degeneracy and make CP measurements. The origin of CP violation in the $K^{0}$ and $B^{0}$ meson systems might lie in the the $H^0/A^0$ Higgs bosons. If large extra dimensions exist, black holes with lifetimes of $\sim 10^{-26}$ seconds could be created and observed via Hawking radiation at the LHC. Unlike proton or electron colliders, muon colliders can produce black hole systems of known mass. This opens the possibilities of measuring quantum remnants, gravitons as missing energy, and scanning production turn on. Proton colliders are hampered by parton distributions and CLIC by beamstrahlung. The ILC lacks the energy reach.

hep-ph↗

arXiv2003

Terabyte IDE RAID-5 Disk Arrays

High energy physics experiments are currently recording large amounts of data and in a few years will be recording prodigious quantities of data. New methods must be developed to handle this data and make analysis at universities possible. We examine some techniques that exploit recent developments in commodity hardware. We report on tests of redundant arrays of integrated drive electronics (IDE) disk drives for use in offline high energy physics data analysis. IDE redundant array of inexpensive disks (RAID) prices now are less than the cost per terabyte of million-dollar tape robots! The arrays can be scaled to sizes affordable to institutions without robots and used when fast random access at low cost is important.

physics.data-an↗

arXiv2001

A Search for Charmless $B\to VV$ Decays

We have studied two-body charmless decays of the $B$ meson into the final states $ρ^0 ρ^0$, $K^{*0} ρ^0$, $K^{*0} K^{*0}$, $K^{*0} \bar{K^{*0}}$, $K^{*+} ρ^0$, $K^{*+} \bar{K^{*0}}$, and $K^{*+} K^{*-}$ using only decay modes with charged daughter particles. Using 9.7 million $B \bar{B}$ pairs collected with the CLEO detector, we place 90% confidence level upper limits on the branching fractions, $(0.46-7.0)\times 10^{-5}$, depending on final state and polarization.

hep-ex↗

arXiv2000

Search for D0-D0B Mixing

We report on a search for D0-D0B mixing made by studying the `wrong-sign' process D0->K^+pi^-. The data come from an integrated luminosity of 9.0 1/fb of e^+e^- collisions at s^(1/2) of approximately 10 GeV recorded with the CLEO II.V detector. We measure the time integrated rate of the `wrong-sign' process D0->K^+pi^- relative to that of the Cabibbo-favored process D0B->K^+pi^- to be R=(0.332^{+0.063}_{-0.065}+-0.040)%. We study D0->K^+pi^- as a function of decay time to distinguish direct doubly Cabibbo-suppressed decay from D0-D0B mixing. The amplitudes that describe D0-D0B mixing, x' and y', are consistent with zero. At the 95% C.L. and without assumptions concerning charge-parity (CP) violating parameters, we find (1/2)x'^2 < 0.041% and -5.8% < y' < 1.0%.

hep-ex↗