arXiv subjects

Y. Gan

Publications and source records attributed to Y. Gan.

5 recordsLinked to original sources

arXiv2026

Test-beam results from MiniCACTUS-v2: A depleted monolithic CMOS timing sensor prototype

MiniCACTUS-v2 is a monolithic sensor prototype designed in LF 150 nm CMOS process for time tagging of individual Minimum Ionizing Particles with an accuracy better than 100 ps. The sensing element is a deep n-well/p-substrate diode without internal amplification. To minimize detector capacitances, the analog front-ends and the discriminators for each pixel have been implemented outside the pixel, at the column level. After fabrication, the sensors have been thinned to 150 microns, 175 microns and 200 microns and then post-processed for backside biasing. The breakdown voltages measured on these sensors are higher than 500 V, ensuring the complete depletion of the charge collection volume. In this paper, we will focus on the time resolution measurements from a test-beam campaign conducted in July 2025 at SPS-CERN. During this period, several pixels from the 3 different sensor thicknesses have been tested at different bias voltages. The best time resolution measured is 48.88 ps on a 0.5 mm x 0.5 mm pixel from a 175 microns-thick sensor at 500 V, with nominal settings for the on-chip analog front-end and discriminator.

physics.ins-det↗

arXiv2021

Three-dimensional vibrations of multilayered hollow spheres submerged in a complex fluid

This paper presents a three-dimensional analytical study of the intrinsic free vibration of an elastic multilayered hollow sphere interacting with an exterior non-Newtonian fluid medium. The fluid is assumed to be characterized by a compressible linear viscoelastic model accounting for both the shear and compressional relaxation processes. For small-amplitude vibrations, the equations governing the viscoelastic fluid can be linearized, which are then solved by introducing appropriate potential functions. The solid is assumed to exhibit a particular material anisotropy, i.e. spherical isotropy, which includes material isotropy as a special case. The equations governing the anisotropic solid are solved in spherical coordinates using the state-space formalism, which finally establishes two separate transfer relations correlating the state vectors at the innermost surface with those at the outermost surface of the multilayered hollow sphere. By imposing the continuity conditions at the fluid-solid interface, two separate analytical characteristic equations are derived, which characterize two independent classes of vibration. Numerical examples are finally conducted to validate the theoretical derivation as well as to investigate the effects of various factors, including fluid viscosity and compressibility, fluid viscoelasticity, solid anisotropy and surface effect, as well as solid intrinsic damping, on the vibration characteristics of the submerged hollow sphere. Particularly, our theoretically predicted vibration frequencies and quality factors of gold nanospheres with intrinsic damping immersed in water agree exceptionally well with the available experimentally measured results. The reported analytical solution is truly and fully three-dimensional, covering from the purely radial breathing mode to torsional mode to any general spheroidal mode.

cond-mat.soft↗

arXiv2020

Exploiting the Planck-Einstein Relation

The origin of quantum physics was the discovery of the base unit of electromagnetic action $h$ by Max Planck in 1900 when he analyzed the experimental results of the black body radiation. This permitted Albert Einstein a few years later to explain the photoelectric effect by the absorption of photons with an energy of $E = h \cdot f$. We exploit the Planck-Einstein relation in a new type of fundamental spectroscopic measurements of direct transitions between two states with energy differences of about 10 neV and induced frequencies of a few MHz. Employing a Lamb-shift polarimeter and a Sona transition unit, featuring a relatively simple magnetic field configuration of two opposing solenoidal coils, we were able to determine $f$ and measure $E$ independently. Only resonances corresponding to integer multiples of Planck's constant $h$ were observed in our setup, which can very well be explained quantitatively by the Schrödinger equation. This new method beautifully demonstrates the quantization in the micro-cosmos and allows one to measure the hyperfine splitting energies between the substates with $F=1$ and $m_F = -1, 0, +1$ of metastable hydrogen atoms as function of a magnetic field and, thus, to investigate the influence of QED corrections on the Breit-Rabi diagram.

physics.atom-ph↗

arXiv2019

Physics case for an LHCb Upgrade II - Opportunities in flavour physics, and beyond, in the HL-LHC era

The LHCb Upgrade II will fully exploit the flavour-physics opportunities of the HL-LHC, and study additional physics topics that take advantage of the forward acceptance of the LHCb spectrometer. The LHCb Upgrade I will begin operation in 2020. Consolidation will occur, and modest enhancements of the Upgrade I detector will be installed, in Long Shutdown 3 of the LHC (2025) and these are discussed here. The main Upgrade II detector will be installed in long shutdown 4 of the LHC (2030) and will build on the strengths of the current LHCb experiment and the Upgrade I. It will operate at a luminosity up to $ 2 \times 10^{34} \rm cm^{-2}s^{-1}$, ten times that of the Upgrade I detector. New detector components will improve the intrinsic performance of the experiment in certain key areas. An Expression Of Interest proposing Upgrade II was submitted in February 2017. The physics case for the Upgrade II is presented here in more depth. $CP$-violating phases will be measured with precisions unattainable at any other envisaged facility. The experiment will probe $b\to s \ell^+\ell^-$ and $b\to d \ell^+\ell^-$ transitions in both muon and electron decays in modes not accessible at Upgrade I. Minimal flavour violation will be tested with a precision measurement of the ratio of $B(B^0\toμ^+μ^-)/B(B_s^0\to μ^+μ^-)$. Probing charm $CP$ violation at the $10^{-5}$ level may result in its long sought discovery. Major advances in hadron spectroscopy will be possible, which will be powerful probes of low energy QCD. Upgrade II potentially will have the highest sensitivity of all the LHC experiments on the Higgs to charm-quark couplings. Generically, the new physics mass scale probed, for fixed couplings, will almost double compared with the pre-HL-LHC era; this extended reach for flavour physics is similar to that which would be achieved by the HE-LHC proposal for the energy frontier.

hep-ex↗

arXiv2013

Emergence of charge density wave domain walls above the superconducting dome in TiSe2

Superconductivity (SC) in so-called "unconventional superconductors" is nearly always found in the vicinity of another ordered state, such as antiferromagnetism, charge density wave (CDW), or stripe order. This suggests a fundamental connection between SC and fluctuations in some other order parameter. To better understand this connection, we used high-pressure x-ray scattering to directly study the CDW order in the layered dichalcogenide TiSe2, which was previously shown to exhibit SC when the CDW is suppressed by pressure [1] or intercalation of Cu atoms [2]. We succeeded in suppressing the CDW fully to zero temperature, establishing for the first time the existence of a quantum critical point (QCP) at Pc = 5.1 +/- 0.2 GPa, which is more than 1 GPa beyond the end of the SC region. Unexpectedly, at P = 3 GPa we observed a reentrant, weakly first order, incommensurate phase, indicating the presence of a Lifshitz tricritical point somewhere above the superconducting dome. Our study suggests that SC in TiSe2 may not be connected to the QCP itself, but to the formation of CDW domain walls.

cond-mat.supr-con↗