arXiv subjects

S. Braun

Publications and source records attributed to S. Braun.

At least 19 recordsLinked to original sources

arXiv2026

An improved direct limit on the muon electric dipole moment

A limit on the permanent electric dipole moment (EDM) of the positive muon is presented based on data from the Fermilab Muon g-2 Experiment taken between 2019 and 2020. The tracking detectors measure the average vertical decay angle of positrons from muon decays, enabling a search for an interaction between a possible muon EDM $d_\mu$ and the lab-frame magnetic field. The result, $d_\mu = (-0.35 \pm 0.19_{\mathrm{stat}} \pm 0.34_{\mathrm{sys}}) \times10^{-19}~e\cdot$cm, is consistent with zero and sets a new direct limit on the muon EDM of $|d_\mu|<1.10\times10^{-19}~e\cdot$cm at the 95 percent confidence level.

hep-ex↗

arXiv2026

Optimization studies of silicon remoTES cryogenic calorimeters

The remoTES design, developed within the COSINUS experiment, enables a broader range of materials to be operated as cryogenic calorimeters read out with Transition Edge Sensors (TESs). In this configuration, the TES is fabricated onto a separate chip and thermally coupled to the absorber via a gold (Au) link. The remoTES concept has been successfully tested on various target materials. To further enhance detector performance and to fully exploit the advantages of the remote coupling design a series of optimization studies has been conducted using silicon (Si) absorbers as benchmark. This work presents an evaluation of several measurements aimed at reducing the thermal boundary resistance and enhancing signal transmission across Si remoTES interfaces, specifically from the absorber to the phonon collector and from the phonon collector to the TES. By testing a new Au link design and three distinct phonon collector configurations, Au, copper, and aluminum (Al)/Au, we achieved a baseline resolution of (21.5 +/- 0.3)eV using the Al/Au phonon collector.

physics.ins-det↗

arXiv2026

Final Report on the Measurement of the Positive Muon Anomalous Magnetic Moment at Fermilab to 127 ppb

This report details the final measurement of the muon magnetic anomaly, $a_{\mu}=(g_{\mu}-2)/2$, by the Muon $g-2$ experiment at Fermi National Accelerator Laboratory (FNAL), using positive muons collected from 2021 to 2023. The value of $a_{\mu}$ is determined from the ratio of the anomalous spin precession frequency to the shielded proton precession frequency in the muon storage ring magnetic field, combined with external constants known at the 22 ppb level. The new dataset, containing over $2.5$ times the statistics of our previous results, yields $a_{\mu}=116\,592\,0710(162)\times 10^{-12}$ (139 ppb), or $a_{\mu}=116\,592\,0705(148)\times 10^{-12}$ (127 ppb) when combined with our previous results. The new experimental world average, dominated by the measurements at FNAL, is $a_{\mu}^{\text{Exp}}=116\,592\,0715(145)\times 10^{-12}$ (124 ppb).

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arXiv2025

Measurement of the Positive Muon Anomalous Magnetic Moment to 127 ppb

A new measurement of the magnetic anomaly $a_{\mu}$ of the positive muon is presented based on data taken from 2020 to 2023 by the Muon $g-2$ Experiment at Fermi National Accelerator Laboratory (FNAL). This dataset contains over 2.5 times the total statistics of our previous results. From the ratio of the precession frequencies for muons and protons in our storage ring magnetic field, together with precisely known ratios of fundamental constants, we determine $a_{\mu} = 116\,592\,0710(162) \times 10^{-12}$ (139 ppb) for the new datasets, and $a_{\mu} = 116\,592\,0705(148) \times 10^{-12}$ (127 ppb) when combined with our previous results. The new experimental world average, dominated by the measurements at FNAL, is $a_{\mu}(\text{exp}) =116\,592\,0715(145) \times 10^{-12}$ (124 ppb). The measurements at FNAL have improved the precision on the world average by over a factor of four.

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arXiv2025

United States Muon Collider Community White Paper for the European Strategy for Particle Physics Update

This document is being submitted to the 2024-2026 European Strategy for Particle Physics Update (ESPPU) process on behalf of the US Muon Collider community, with its preparation coordinated by the interim US Muon Collider Coordination Group. The US Muon Collider Community comprises a few hundred American scientists. The purpose of the document is to inform ESPPU about the US plans for Muon Collider research and development (R&D), explain how these efforts align with the broader international R&D initiatives, and present the US community vision for the future realization of this transformative project.

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arXiv2025

Measured gain suppression in FBK LGADs with different active thicknesses

In recent years, the gain suppression mechanism has been studied for large localized charge deposits in Low-Gain Avalanche Detectors (LGADs). LGADs are a thin silicon detector with a highly doped gain layer that provides moderate internal signal amplification. Using the CENPA Tandem accelerator at the University of Washington, the response of LGADs with different thicknesses to MeV-range energy deposits from a proton beam were studied. Three LGAD prototypes of 50~$\mu$m, 100~$\mu$m, 150~$\mu$m were characterized. The devices' gain was determined as a function of bias voltage, incidence beam angle, and proton energy. This study was conducted in the scope of the PIONEER experiment, an experiment proposed at the Paul Scherrer Institute to perform high-precision measurements of rare pion decays. LGADs are considered for the active target (ATAR) and energy linearity is an important property for particle ID capabilities.

physics.ins-det↗

arXiv2024

Gain suppression study on LGADs at the CENPA tandem accelerator

Low-Gain Avalanche Detectors (LGADs) are a type of thin silicon detector with a highly doped gain layer that provides moderate internal signal amplification. One recent challenge in the use of LGADs, studied by several research groups, is the gain suppression mechanism for large localized charge deposits. Using the CENPA Tandem accelerator at the University of Washington, the response of the LGADs to MeV-range energy deposits from a proton beam was studied. Two LGAD prototypes and a PIN diode were characterized, and the gain of the devices was determined as a function of bias voltage, incidence beam angle and proton energy. This study was conducted in the scope of the PIONEER experiment, an experiment proposed at the Paul Scherrer Institute to perform high-precision measurements of rare pion decays. %At the center of the experiment, a high-granularity active target (ATAR) will stop the pion and characterize its decay. A range of deposited charge from Minimum Ionizing Particle (MIP, few 10s of KeV) from positrons to several MeV from the stopping pions/muons is expected in PIONEER; the detection and separation of close-by hits in such a wide dynamic range will be a main challenge of the experiment. To achieve this goal, the gain suppression mechanism has to be understood fully.

physics.ins-det↗

arXiv2024

Detailed Report on the Measurement of the Positive Muon Anomalous Magnetic Moment to 0.20 ppm

We present details on a new measurement of the muon magnetic anomaly, $a_\mu = (g_\mu -2)/2$. The result is based on positive muon data taken at Fermilab's Muon Campus during the 2019 and 2020 accelerator runs. The measurement uses $3.1$ GeV$/c$ polarized muons stored in a $7.1$-m-radius storage ring with a $1.45$ T uniform magnetic field. The value of $ a_{\mu}$ is determined from the measured difference between the muon spin precession frequency and its cyclotron frequency. This difference is normalized to the strength of the magnetic field, measured using Nuclear Magnetic Resonance (NMR). The ratio is then corrected for small contributions from beam motion, beam dispersion, and transient magnetic fields. We measure $a_\mu = 116 592 057 (25) \times 10^{-11}$ (0.21 ppm). This is the world's most precise measurement of this quantity and represents a factor of $2.2$ improvement over our previous result based on the 2018 dataset. In combination, the two datasets yield $a_\mu(\text{FNAL}) = 116 592 055 (24) \times 10^{-11}$ (0.20 ppm). Combining this with the measurements from Brookhaven National Laboratory for both positive and negative muons, the new world average is $a_\mu$(exp) $ = 116 592 059 (22) \times 10^{-11}$ (0.19 ppm).

hep-ex↗

arXiv2023

Measurement of the Positive Muon Anomalous Magnetic Moment to 0.20 ppm

We present a new measurement of the positive muon magnetic anomaly, $a_\mu \equiv (g_\mu - 2)/2$, from the Fermilab Muon $g\!-\!2$ Experiment using data collected in 2019 and 2020. We have analyzed more than 4 times the number of positrons from muon decay than in our previous result from 2018 data. The systematic error is reduced by more than a factor of 2 due to better running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, $\tilde{\omega}'^{}_p$, and of the anomalous precession frequency corrected for beam dynamics effects, $\omega_a$. From the ratio $\omega_a / \tilde{\omega}'^{}_p$, together with precisely determined external parameters, we determine $a_\mu = 116\,592\,057(25) \times 10^{-11}$ (0.21 ppm). Combining this result with our previous result from the 2018 data, we obtain $a_\mu\text{(FNAL)} = 116\,592\,055(24) \times 10^{-11}$ (0.20 ppm). The new experimental world average is $a_\mu (\text{Exp}) = 116\,592\,059(22)\times 10^{-11}$ (0.19 ppm), which represents a factor of 2 improvement in precision.

hep-ex↗

arXiv2021

Search for the doubly charmed baryon $\itΩ_{cc}^{+}$

A search for the doubly charmed baryon $\itΩ_{cc}^{+}$ with the decay mode $\itΩ_{cc}^{+}\to\itΞ_c^{+}K^{-}π^{+}$ is performed using proton-proton collision data at a centre-of-mass energy of 13$\mathrm{\,Te\kern -0.1em V}$ collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of $5.4\,\mathrm{fb}^{-1}$. No significant signal is observed within the invariant mass range of 3.6 to 4.0$\mathrm{\,Ge\kern -0.1em V}/c^2$. Upper limits are set on the ratio $R$ of the production cross-section times the total branching fraction of the $\itΩ_{cc}^{+}\to\itΞ_c^{+}K^{-}π^{+}$ decay with respect to the $\itΞ_{cc}^{++}\to\itΛ_c^{+}K^{-}π^{+}π^{+}$ decay. Upper limits at 95% credibility level for $R$ in the range $0.005$ to $0.11$ are obtained for different hypotheses on the $\itΩ_{cc}^{+}$ mass and lifetime in the rapidity range from 2.0 to 4.5 and transverse momentum range from 4 to 15$\mathrm{\,Ge\kern -0.1em V}/c$.

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arXiv2021

Search for the doubly heavy baryons $\itΩ_{bc}^{\rm0}$ and $\itΞ_{bc}^{\rm0}$ decaying to $\it{Λ_{c}^{+}π^{-}}$ and $\it{Ξ_{c}^{+}π^{-}}$

The first search for the doubly heavy $\itΩ_{bc}^{\rm0}$ baryon and a search for $\itΞ_{bc}^{\rm0}$ baryon are performed using $pp$ collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of $13TeV$, corresponding to an integrated luminosity of 5.2$fb^{-1}$. The baryons are reconstructed via their decays to $\it{Λ_{c}^{+}π^{-}}$ and $\it{Ξ_{c}^{+}π^{-}}$. No significant excess is found for invariant masses between 6700 and 7300$MeV/c^2$, in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20$GeV/c$. Upper limits are set on the ratio of the $\itΩ_{bc}^{\rm0}$ and $\itΞ_{bc}^{\rm0}$ production cross-section times the branching fraction to $\it{Λ_{c}^{+}π^{-}}$ ($\it{Ξ_{c}^{+}π^{-}}$) relative to that of the $\it{Λ_b^{\rm0}}$ ($\it{Ξ_b^{\rm0}}$) baryon, for different lifetime hypotheses, at $95\%$ confidence level. The upper limits range from $0.5\times10^{-4}$ to $2.5\times10^{-4}$ for the $\itΩ_{bc}^{\rm0}\rightarrow\it{Λ_{c}^{+}π^{-}}$ ($\itΞ_{bc}^{\rm0}\rightarrow\it{Λ_{c}^{+}π^{-}}$) decay, and from $1.4\times10^{-3}$ to $6.9\times10^{-3}$ for the $\itΩ_{bc}^{\rm0}\rightarrow\it{Ξ_{c}^{+}π^{-}}$ ($\itΞ_{bc}^{\rm0}\rightarrow\it{Ξ_{c}^{+}π^{-}}$) decay, depending on the considered mass and lifetime of the $\itΩ_{bc}^{\rm0}$ ($\itΞ_{bc}^{\rm0}$) baryon.

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arXiv2021

Study of coherent $J/\psi$ production in lead-lead collisions at $\sqrt{s_{NN}} = 5 TeV$

Coherent production of $J/\psi$ mesons is studied in ultraperipheral lead-lead collisions at a nucleon-nucleon centre-of-mass energy of 5 TeV, using a data sample collected by the LHCb experiment corresponding to an integrated luminosity of about $10 \mu b^{-1}$. The $J/\psi$ mesons are reconstructed in the dimuon final state and are required to have transverse momentum below 1 GeV. The cross-section within the rapidity range of $2.0 < y < 4.5$ is measured to be $4.45\pm0.24\pm0.18\pm0.58$ mb, where the first uncertainty is statistical, the second systematic and the third originates from the luminosity determination. The cross-section is also measured in $J/\psi$ rapidity intervals. The results are compared to predictions from phenomenological models.

hep-ex↗

arXiv2021

Measurement of the shape of the $B_s^0\rightarrow D_s^{*-}μ^{+}ν_μ$ differential decay rate

The shape of the $B_s^0\rightarrow D_s^{*-}μ^+ν_μ$ differential decay rate is obtained as a function of the hadron recoil using proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 fb$^{-1}$ collected by the LHCb detector. The $B_s^0\rightarrow D_s^{*-}μ^+ν_μ$ decay is reconstructed through the decays $D_s^{*-}\rightarrow D_s^{-}γ$ and $D_s^{-}\rightarrow K^-K^+π^-$. The differential decay rate is fitted with the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) parametrisations of the form factors, and the relevant quantities for both are extracted.

hep-ex↗

arXiv2021

Measurement of branching fraction ratios for $B^+\to D^{+}D^-K^+$, $B^+\to D^{-}D^+K^+$, and $B^0\to D^{*-}D^0K^+$ decays

A measurement of four branching-fraction ratios for three-body decays of $B$ mesons involving two open-charm hadrons in the final state is presented. Run 1 and Run 2 $pp$ collision data are used, recorded by the LHCb experiment at centre-of-mass energies $7$, $8$, and $13$ TeV and corresponding to an integrated luminosity of $9$ fb$^{-1}$. The measured branching-fraction ratios are \[ \begin{eqnarray} \frac{\mathcal{B} (B^+\to D^{*+}D^-K^+)}{\mathcal{B} (B^+\to \kern 0.2em\overline{\kern -0.2em D}{}^0 D^0 K^+)} &=& 0.517 \pm 0.015 \pm 0.013 \pm 0.011 , \\ \frac{\mathcal{B} (B^+\to D^{*-}D^+K^+)}{\mathcal{B} (B^+\to \kern 0.2em\overline{\kern -0.2em D}{}^0 D^0 K^+)} &=& 0.577 \pm 0.016 \pm 0.013 \pm 0.013 , \\ \frac{\mathcal{B} (B^0\to D^{*-}D^0K^+)}{\mathcal{B} (B^0\to D^- D^0 K^+)} &=& 1.754 \pm 0.028 \pm 0.016 \pm 0.035 , \\ \frac{\mathcal{B} (B^+\to D^{*+}D^-K^+)}{\mathcal{B} (B^+\to D^{*-}D^+K^+)} &=& 0.907 \pm 0.033 \pm 0.014 ,\end{eqnarray} \] where the first of the uncertainties is statistical, the second systematic, and the third is due to the uncertainties on the $D$-meson branching fractions. These are the most accurate measurements of these ratios to date.

hep-ex↗

arXiv2020

Measurement of the branching fraction of the decay $B_s^0\to K_S^0 K_S^0$

A measurement of the branching fraction of the decay $B_s^0 \to K_S^0 K_S^0$ is performed using proton-proton collision data corresponding to an integrated luminosity of 5 $fb^{-1}$ collected by the LHCb experiment between 2011 and 2016. The branching fraction is determined to be BR($B_s^0 \to K_S^0 K_S^0$) = [8.3 $\pm$ 1.6 (stat) $\pm$ 0.9 (syst) $\pm$ 0.8 (norm) $\pm$ 0.3 ($f_s/f_d$)] $\times 10^{-6}$ , where the first uncertainty is statistical, the second is systematic, and the third and fourth are due to uncertainties on the branching fraction of the normalization mode $B^0 \to ϕK_S^0$ and the ratio of hadronization fractions $f_s/f_d$. This is the most precise measurement of this branching fraction to date. Furthermore, a measurement of the branching fraction of the decay $B^0 \to K_S^0 K_S^0$ is performed relative to that of the $B_s^0 \to K_S^0 K_S^0$ channel, and is found to be $\frac{BR(B^0 \to K_S^0 K_S^0)}{BR(B_s^0 \to K_S^0 K_S^0)}$ = [7.5 $\pm$ 3.1 (stat) $\pm$ 0.5 (syst) $\pm$ 0.3 ($f_s/f_d$)] $\times 10^{-2}$.

hep-ex↗

arXiv2020

Measurement of psi(2S) production cross-sections in proton-proton collisions at 7 and 13 TeV

The cross-sections of $ψ(2S)$ meson production in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$ are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of $275~p\mathrm{b}^{-1}$. The production cross-sections for prompt $ψ(2S)$ mesons and those for $ψ(2S)$ mesons from $b$-hadron decays ($ψ{(2S)}\mathrm{-from-}b$) are determined as functions of the transverse momentum, $p_{\mathrm{T}}$, and the rapidity, $y$, of the $ψ(2S)$ meson in the kinematic range $2<p_{\mathrm{T}}<20~\mathrm{GeV}/c$ and $2.0<y<4.5$. The production cross-sections integrated over this kinematic region are \begin{equation*} \begin{split} σ(\mbox{prompt }ψ(2S),13~\mathrm{TeV}) &= {1.430 \pm 0.005(\mathrm{stat}) \pm 0.099 (\mathrm{syst})μ\mathrm{b}},\\ σ(ψ(2S)\mathrm{-from-}b,13~\mathrm{TeV})&={0.426 \pm 0.002(\mathrm{stat}) \pm0.030 (\mathrm{syst})μ\mathrm{b}}. \end{split} \end{equation*} A new measurement of $ψ(2S)$ production cross-sections in $pp$ collisions at $\sqrt{s}=7~\mathrm{TeV}$ is also performed using data collected in 2011, corresponding to an integrated luminosity of $614~{p\mathrm{b}^{-1}}$.The integrated production cross-sections in the kinematic range $3.5<p_{\mathrm{T}}<14~\mathrm{GeV}/c$ and $2.0<y<4.5$ are \begin{equation*} \begin{split} σ(\mbox{prompt }ψ(2S),7~\mathrm{TeV}) &={0.471 \pm0.001 (\mathrm{stat}) \pm 0.025 (\mathrm{syst})μ\mathrm{b}},\\ σ(ψ(2S)\mathrm{-from-}b,7~\mathrm{TeV}) &={0.126\pm0.001 (\mathrm{stat}) \pm0.008 (\mathrm{syst})μ\mathrm{b}}. \end{split} \end{equation*} All results show reasonable agreement with theoretical calculations.

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arXiv2020

Precision measurement of the $B_{c}^{+}$ meson mass

A precision measurement of the $B_{c}^{+}$ meson mass is performed using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of $7, 8$ and $13$ TeV, corresponding to a total integrated luminosity of $9.0 \,{\rm fb}^{-1}$. The $B_{c}^{+}$ mesons are reconstructed via the decays $B_{c}^{+} \rightarrow J\mskip -3mu/\mskip -2muψ\mskip 2mu π^+$, $B_{c}^{+} \rightarrow J\mskip -3mu/\mskip -2muψ\mskip 2mu π^+ π^- π^+$, $B_{c}^{+} \rightarrow J\mskip -3mu/\mskip -2muψ\mskip 2mu p \bar{p} π^+$, $B_{c}^{+} \rightarrow J\mskip -3mu/\mskip -2muψ\mskip 2mu D_{s}^{+}$, $B_{c}^{+} \rightarrow J\mskip -3mu/\mskip -2muψ\mskip 2mu D^{0} K^{+}$ and $B_{c}^{+} \rightarrow B_{s}^{0} π^{+}$. Combining the results of the individual decay channels, the $B_{c}^{+}$ mass is measured to be $6274.47 \pm 0.27 \,({\rm stat}) \pm 0.17 \,({\rm syst}) \mathrm{\,Me\kern -0.1em V}/c^{2}$. This is the most precise measurement of the $B_{c}^{+}$ mass to date. The difference between the $B_{c}^{+}$ and $B_{s}^{0}$ meson masses is measured to be $907.75 \pm 0.37 \,({\rm stat}) \pm 0.27 \,({\rm syst}) \mathrm{\,Me\kern -0.1em V}/c^{2}$.

hep-ex↗

arXiv2020

Measurement of $C\!P$-averaged observables in the $B^{0}\rightarrow K^{*0}μ^{+}μ^{-}$ decay

An angular analysis of the $B^{0}\rightarrow K^{*0}(\to K^{+}π^{-})μ^{+}μ^{-}$ decay is presented using a data set corresponding to an integrated luminosity of 4.7 fb$^{-1}$ of $pp$ collision data collected with the LHCb experiment. The full set of $C\!P$-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the $K^{+}π^{-}$ system in an S-wave configuration is taken into account. The tension seen between the previous LHCb results and the Standard Model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters.

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