Searcharxiv⌕ Search

arXiv subjects

Gerald Eigen

Publications and source records attributed to Gerald Eigen.

At least 19 recordsLinked to original sources
arXiv2020

Light Yield and Uniformity Measurements of Different Scintillator Tiles with Silicon Photomultipliers

We present light yield and uniformity measurements of square and hexagonal tiles read out with silicon photomultipliers via a Y11 wavelength-shifting fiber or directly from the side or from the center at the top face. All tiles are 3~mm thick and have an area of $\rm 9~cm^2$. The sides are wrapped with two layers of Teflon tape while top and bottom faces are covered with two layers of Tyvec paper. We further show the first light yield and uniformity measurements of ATLAS Tile Calorimeter (TileCal) tiles with MPPC readout. This study has been motivated by looking into a possible phase 3 upgrade for the ATLAS hadron calorimeter and for hadron calorimeters at future hadron colliders.

physics.ins-det↗
arXiv2019

Recent Results on $\tau$ Decays

We present herein new results from Belle on the $\tau^- \rightarrow \pi^- \nu_{\rm \tau} \ell^+ \ell^- $ branching fraction and from BABAR on the $\tau^- \rightarrow K^- (0,1,2,3) \pi^0 \nu_{\rm \tau}$, $\tau^- \rightarrow \pi^- (3,4) \pi^0 \nu_{\rm \tau}$ and $\tau^- \rightarrow K^- K^0_{\rm S} \nu_{\rm \tau}$ branching fractions. From the $K^- K^0_{\rm S}$ mass spectrum we determine the spectral function. The improved branching fraction measurements of the $\tau^- \rightarrow K^- (0,1,2,3) \pi^0 \nu_{\rm \tau}$ decays are used to determine $|V_{\rm us}|$ from $\tau^- \rightarrow X_{\rm s}^- \nu_{\rm \tau}$ inclusive decays.

hep-ex↗
arXiv2019

The International Linear Collider. A European Perspective

The International Linear Collider (ILC) being proposed in Japan is an electron-positron linear collider with an initial energy of 250 GeV. The ILC accelerator is based on the technology of superconducting radio-frequency cavities. This technology has reached a mature stage in the European XFEL project and is now widely used. The ILC will start by measuring the Higgs properties, providing high-precision and model-independent determinations of its parameters. The ILC at 250 GeV will also search for direct new physics in exotic Higgs decays and in pair-production of weakly interacting particles. The use of polarised electron and positron beams opens new capabilities and scenarios that add to the physics reach. The ILC can be upgraded to higher energy, enabling precision studies of the top quark and measurement of the top Yukawa coupling and the Higgs self-coupling. The international -- including European -- interest for the project is very strong. Europe has participated in the ILC project since its early conception and plays a major role in its present development covering most of its scientific and technological aspects: physics studies, accelerator and detectors. The potential for a wide participation of European groups and laboratories is thus high, including important opportunities for European industry. Following decades of technical development, R&D, and design optimisation, the project is ready for construction and the European particle physics community, technological centers and industry are prepared to participate in this challenging endeavour.

hep-ex↗
arXiv2019

The International Linear Collider. A Global Project

A large, world-wide community of physicists is working to realise an exceptional physics program of energy-frontier, electron-positron collisions with the International Linear Collider (ILC). This program will begin with a central focus on high-precision and model-independent measurements of the Higgs boson couplings. This method of searching for new physics beyond the Standard Model is orthogonal to and complements the LHC physics program. The ILC at 250 GeV will also search for direct new physics in exotic Higgs decays and in pair-production of weakly interacting particles. Polarised electron and positron beams add unique opportunities to the physics reach. The ILC can be upgraded to higher energy, enabling precision studies of the top quark and measurement of the top Yukawa coupling and the Higgs self-coupling. The key accelerator technology, superconducting radio-frequency cavities, has matured. Optimised collider and detector designs, and associated physics analyses, were presented in the ILC Technical Design Report, signed by 2400 scientists. There is a strong interest in Japan to host this international effort. A detailed review of the many aspects of the project is nearing a conclusion in Japan. Now the Japanese government is preparing for a decision on the next phase of international negotiations, that could lead to a project start within a few years. The potential timeline of the ILC project includes an initial phase of about 4 years to obtain international agreements, complete engineering design and prepare construction, and form the requisite international collaboration, followed by a construction phase of 9 years.

hep-ex↗
arXiv2017

Exclusion of multifold solutions of the CKM Unitarity Triangle by a time-dependent Dalitz plot analysis of $\bar B^0 \to D^{(*)0} h^0$ with $D^0 \to K^0_S \pi^+ \pi^-$ decays combining BABAR and Belle data

We present results of a new analysis campaign, which combines the final data samples collected by the B factory experiments BABAR and Belle in single physics analyses to achieve a unique sensitivity in time-dependent \CP\ violation measurements. The data samples contain $(471 \pm 3) \times 10^6 ~B \bar B$ pairs recorded by the BABAR detector and $(772 \pm 11) \times 10^6 ~ B \bar B$ pairs recorded by the Belle detector in $e^+e^-$ collisions at the center-of-mass energies corresponding to the mass of the $\Upsilon(4S)$ resonance at the asymmetric-energy $B$ factories PEP-II at SLAC and KEKB at KEK, respectively. We present a measurement of $\sin 2\beta $ and $\cos 2\beta $ by a time-dependent Dalitz plot analysis of $B^0 \to D^{(*)} h^0$ with $D \to K^0_S \pi^+\pi^-$ decays. A first evidence for $\cos 2\beta >0$, the exclusion of trigonometric multifold solutions of the Unitarity Triangle and an observation of \CP\ violation are reported.

hep-ex↗
arXiv2017

Gain Stablization of SiPMs

The gain of silicon photomultipliers (SiPMs) increases with bias voltage and decreases with temperature. To operate SiPMs at stable gain, the bias voltage can be adjusted to compensate temperature changes. We have tested this concept with 30 SiPMs from three manufacturers (Hamamatsu, KETEK, CPTA) in a climate chamber at CERN varying the temperature from $1^\circ \rm C$ to $50^\circ \rm C$. We built an adaptive power supply that used a linear temperature dependence of the bias voltage readjustment. With one selected bias voltage readjustment, we stabilized four SiPMs simultaneously. We fulfilled our goal of limiting the deviation from gain stability in the $20^\circ \rm C-30^\circ C$ temperature range to less than $\pm 0.5\%$ for most of the tested SiPMs. We have studied afterpulsing of SiPMs for different temperatures and bias voltages.

physics.ins-det↗
arXiv2016

SiPM Gain Stabilization Studies for Adaptive Power Supply

We present herein gain stabilization studies of SiPMs using a climate chamber at CERN. We present results for four detectors not tested before, three from Hamamatsu and one from KETEK. Two of the Hamamatsu SiPMs are novel sensors with trenches that reduce cross talk. We use an improved readout system with a digital oscilloscope controlled with a dedicated LabView program. We improved and automized the analysis to deal with large datasets. We have measured the gain-versus-bias-voltage dependence at fixed temperature and gain-versus-temperature dependence at fixed bias voltage to determine the bias voltage dependence on temperature $V(T)$ for stable gain. We show that the gain remains stable to better than $\pm 0.5\%$ in the $20^\circ \rm C - 30^\circ C$ temperature range if the bias voltage is properly adjusted with temperature.

physics.ins-det↗
arXiv2015

Study of B ->K pi pi gamma Decays

Using $471 \times 10^6 ~B \bar B$ decays recorded with the \babar\ detector at the PEP-II $e^+ e^-$ storage ring, we present the time-dependent \CP\ asymmetry measurement in the radiative penguin decay mode $B^0 \rightarrow K^0_S \rho(770)^0 \gamma$, yielding $S_{K^0_S \rho^0 \gamma} =-0.17\pm 0.32^{+0.07}_{-0.06}$. Since the result is extracted from the time-dependent \CP~asymmetry parameters $S_{K^0_S \pi^+ \pi^- \gamma} =0.14\pm 0.25^{+0.04}_{-0.03}$ and $C _{K^0_S \pi^+ \pi^- \gamma} =-0.39\pm $ measured in the neutral decay $B^0 \rightarrow K^0_S \pi^+ \pi^- \gamma$, we need to correct for the dilution of $K^*(892) \pi \gamma$ in $K \rho \gamma$. The dilution factor $ D_{K^0_S \rho \gamma} =-0.79^{+0.18}_{-0.17}$ is determined from a study of the charged mode $B^+ \rightarrow K^+ \pi^+\pi^-\gamma$, which produces more signal events and is related to the neutral mode by isospin. We need detailed knowledge of the resonance structure in the $K^+ \pi^+ \pi^-$ mass spectrum and measure branching fractions of different resonances to $K \pi$ and $\pi \pi$ final states. We also measure the branching fractions ${\cal B} (B^+ \rightarrow K^+ \pi^+ \pi^- \gamma)= (27.2\pm 1.0 \pm 1.2) \times 10^{-6}$ and ${\cal B} (B^0 \rightarrow K^0_S \pi^+ \pi^- \gamma)= (24.0\pm 2.4^{+1.7}_{-1.8}) \times 10^{-6}$.

hep-ex↗
arXiv2015

Recent BABAR Results

We present herein the most recent BABAR results on direct CP asymmetry measurements in B -> Xs gamma, on partial branching fraction and CP asymmetry measurements in B -> Xs l+l-, on a search for B -> pi/eta l+l- decays, on a search for lepton number violation in B -> X-l+l'+ modes and a study of B-> omega omega and B-> omega phi decays.

hep-ex↗
arXiv2014

Gain Stabilization of SiPMs

The gain of SiPMs depends both on bias voltage and on temperature. For stable operations, both need to be kept constant. In an ILC calorimeter with millions of channels, this is a challenging task. It is, therefore, desirable to compensate for temperature variations by automatically readjusting the bias voltage. We have designed a bias voltage regulator board to achieve this task. We anticipate an uncertainty on the gain stability at the level of $< 1\%$. First, we present measurements of the gain dependence on temperature and bias voltage for several SiPMs from three different manufacturers and determine their dV/dT dependence. Next, we demonstrate the performance of the gain stability with the bias voltage regulator test board on four SiPMs.

physics.ins-det↗
arXiv2013

Global CKM Fits with the Scan Method

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 $\bar ρ- \bar η$ plane using the standard input measurements (CKM matrix elements, $\sin2 β, B^0_{d,s}$ mixing, $ε_K$) as well as branching fraction and \CP asymmetry measurements of B decays to $PP, PV, VV$, and $a_1 P$ final states to determine $α$, $D^{(*)}K^{(*)}$ modes to determine $γ$, and $D^{(*)}π$ and $Dρ$ modes to determine $2β+γ$. 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 $α$ and $β$ as well as between $γ$ and $β$.

hep-ex↗
arXiv2013

Physics at the CLIC e+e- Linear Collider -- Input to the Snowmass process 2013

This paper summarizes the physics potential of the CLIC high-energy e+e- linear collider. It provides input to the Snowmass 2013 process for the energy-frontier working groups on The Higgs Boson (HE1), Precision Study of Electroweak Interactions (HE2), Fully Understanding the Top Quark (HE3), as well as The Path Beyond the Standard Model -- New Particles, Forces, and Dimensions (HE4). It is accompanied by a paper describing the CLIC accelerator study, submitted to the Frontier Capabilities group of the Snowmass process.

hep-ex↗
arXiv2013

Radiative Penguin Decays at e^+ e^- Colliders

In this review, the most recent results of the radiative decays B -> X_s gamma, B -> K^{(*)} l^+ l^-$ and B -> pi/eta l^+ l^- at e^+e^- colliders are discussed. The new, most precise CP asymmetry measurements in B -> X_s gamma from BABAR are presented together with branching fractions and photon energy moments. For B -> K^{(*)} l^+ l^- modes, B factory results on partial branching fractions, rate asymmetries and angular observables are combined with measurements from CDF and the LHC experiments. The first branching fraction upper limits for B -> eta l^+ l^- are shown along with updated upper limits of B -> pi l^+ l^- branching fractions.

hep-ex↗
arXiv2011

B \to K(*)l+l- from B-factories and Tevatron

BABAR and Belle measurements of branching fractions, rate asymmetries and angular observables in the decay modes B \to K(*)l+l- are reviewed and new results from CDF on B \to K(*)μ+μ- branching fractions and angular observables are discussed. A first search for B+ \to K+τ+τ- is presented.

hep-ex↗
arXiv2009

Results on Searches for New Physics at B Factories

We summarize recent results on B+ -> tau+ nu setting constraints on the charged Higgs mass, discuss the CP puzzle in B -> K pi decays and present searches for a light neutral Higgs in radiative Upsilon(2S) and Upsilon(3S)decays.

hep-ex↗
arXiv2001

Performance of Multipurpose Detectors in Super B Factories

Based on background measurements at PEP II the impact of machine-related backgrounds on individual components of multipurpose detectors is examined, that operate in an asymmetric B factory at luminosities up to 10^{36} cm^{-2} s^{-1}. Extrapolations of the BABAR experience suggests two feasible detector designs.

hep-ex↗