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The electroweak b → sll ( l = e, µ ) transition is a flavor-changing neutral current process that mediates through a one-loop penguin diagram. The decay is considered to be a good probe for the New Physics as particles predicted in the beyond Standard Model theories can enter into the loop. The exclusive decay B → K (*) l + l − was first observed by the Belle experiment and it provides many observables such as the branching fraction, CP asymmetry, forward-backward asymmetry, and other angular observables. Recently, the LHCb experiment has reported some clue of a lepton flavor universality violation from the branching fraction ratio of the B → Kµ + µ − and B → Ke + e − decays. In this presentation, we report the status of the B → Kl + l − decay analysis at the Belle II experiment which started the data taking in 2019. We also, present an activity at the Belle II Chulalongkorn University group where we study the B → KJ/ψ decay which has the same topology as the B → Kl + l − .

The Colorado Learning Attitudes about Science Survey, CLASS, has been used as a tool to measure respondents' beliefs or attitudes about physics and how they learn physics. It is composed of 42 Likert scale (strongly disagree to strongly agree) type questions which is classified into 8 categories, which are real world connections, conceptual connections, personal interest, sense making, applied conceptual understanding, problem solving general, problem solving confidence and problem solving sophistication. In this study, we asked 196 high school physics teachers and 211 students from 195 secondary schools in Thailand to respond to this survey along with a 6-open-ended-question survey. In this paper, we focus on two topics: \"What is the difficulty in learning/teaching physics?\" and \"What is the goal in learning/teaching physics?\" We found that physics teachers agree with the experts in most categories, except conceptual connections, applied conceptual understanding and problem solving sophistication. While students tend to disagree with the experts in both conceptual categories and all 3 categories in problem solving. We then compare teachers' to students' responses from these two open-ended questions. On the difficulty aspect: 19% of students believe that difficulty in learning physics is due to incomprehension of physics concept. While 43% of teachers thought that difficulty in teaching physics is because of insufficiency of mathematics background. On the goals aspect, 37% of students aim to enter the university; while 50% of teachers target on helping student to better understand physics.

The 3D range-modulator is a device used in particle delivery systems that can create a highly conformal and homogeneous dose distribution in the target volume with mono-energetic beams, providing an option for high dose-rate FLASH therapy. In the normal case, the modulators are positioned at a typical distance of 30-50 cm in front of the target in order to avoid the fluence ripples resulting from the periodic structure of the modulators. FLUKA Monte Carlo simulation package was used to investigate the fluence distributions of protons penetrating through the 2D range-modulator, the simplified version of the 3D range-modulator, and to determine the minimum distance at which the fluence is homogeneous enough for the treatment. To implement the complex geometry of the modulator in FLUKA, a dedicated FLUKA user routine was developed for the simulation of the periodic pin structures. The highest fluence ripple occurred at a few centimetres behind the modulators and then faded away as the distance increased, which can be described by the edge-scattering effect and later by the blur-out of the overlapping contributions from the pins. Moreover, the dose distribution in water was investigated, particularly for small distances between the modulators and the water phantom. Furthermore, the Monte Carlo results were compared with radiochromic film measurements irradiated with a 3D-printed range modulator and showed a good qualitative agreement. Prospectively, for low modulator-to-target distances, the strong dose inhomogeneities which appear in the proximal part of the target, could introduce additionally a kind of ‘mini beam’ normal-tissue sparing by the 3D range-modulators.

In Particle Data Analysis laboratory activity, aimed at undergraduate and high school students, the student is tasked with classifying collision events which contain two muons decaying from J/ψ meson. The activity provides 2000 collision events from the CMS detector, selected by CMS outreach community. However, classifying 2000 collision events by hand can be a tedious task for any human, so a smaller subset of collision events are usually used in the activity to save time. We built a machine learning classifier which mimic the student's classification based on a subset of collision events handed to the student, using some information from data in corresponding collision event. The information used in this system is parts of muon trajectory, extracted from files suited for CMS event viewer on the internet, as well as the four-momentum of both muons, available from the same source. With this system, students can input a subset of graded events into the system, and the system will be able to illustrate the results if the student worked on all 2000 collision events using his/her logic. Users can download the code from our repository and follow easy instructions to replicate this activity.

Precision spectroscopy of the electron spectrum of the tritium β -decay near the kinematic endpoint is a direct method to determine the effective electron antineutrino mass. The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to determine this quantity with a sensitivity of better than 0.3 eV ( 90 %  C.L.). An inhomogeneous electric potential in the tritium source of KATRIN can lead to distortions of the β -spectrum, which directly impact the neutrino-mass observable. This effect can be quantified through precision spectroscopy of the conversion-electrons of co-circulated metastable 83 m Kr . Therefore, dedicated, several-weeks long measurement campaigns have been performed within the KATRIN data taking schedule. In this work, we infer the tritium source potential observables from these measurements, and present their implications for the neutrino-mass determination.

Precision spectroscopy of the electron spectrum of the tritium$$\\upbeta $$β -decay near the kinematic endpoint is a direct method to determine the effective electron antineutrino mass. The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to determine this quantity with a sensitivity of better than$${0.3}{\\hbox { eV}}$$0.3 eV ($$90\\%$$90 %  C.L.). An inhomogeneous electric potential in the tritium source of KATRIN can lead to distortions of the$$\\upbeta $$β -spectrum, which directly impact the neutrino-mass observable. This effect can be quantified through precision spectroscopy of the conversion-electrons of co-circulated metastable$$^{83\\text {m}}\\text {Kr}$$83 m Kr . Therefore, dedicated, several-weeks long measurement campaigns have been performed within the KATRIN data taking schedule. In this work, we infer the tritium source potential observables from these measurements, and present their implications for the neutrino-mass determination.

Precision spectroscopy of the electron spectrum of the tritium β-decay near the kinematic endpoint is a direct method to determine the effective electron antineutrino mass. The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to determine this quantity with a sensitivity of better than 0.3 eV (90% C.L.). An inhomogeneous electric potential in the tritium source of KATRIN can lead to distortions of the β-spectrum, which directly impact the neutrino-mass observable. This effect can be quantified through precision spectroscopy of the conversion-electrons of co-circulated metastable 83mKr. Therefore, dedicated, several-weeks long measurement campaigns have been performed within the KATRIN data taking schedule. In this work, we infer the tritium source potential observables from these measurements, and present their implications for the neutrino-mass determination.

The projected sensitivity of the effective electron neutrino-mass measurement with the KATRIN experiment is below 0.3 eV (90 % CL) after 5 years of data acquisition. The sensitivity is affected by the increased rate of the background electrons from KATRIN’s main spectrometer. A special shifted-analysing-plane (SAP) configuration was developed to reduce this background by a factor of two. The complex layout of electromagnetic fields in the SAP configuration requires a robust method of estimating these fields. We present in this paper a dedicated calibration measurement of the fields using conversion electrons of gaseous 83mKr, which enables the neutrino-mass measurements in the SAP configuration.

Inelastic dark matter models that have two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limits. The mass splitting between the two dark matter particles \\(\\chi_{1}\\) and \\(\\chi_{2}\\), with \\(m(\\chi_{2}) > m(\\chi_{1})\\), is induced by a dark Higgs field and a corresponding dark Higgs boson \\(h^{\\prime}\\). We present a search for dark matter in events with two vertices, at least one of which must be displaced from the interaction region, and missing energy. Using a \\(365\\,\\mbox{fb}^{-1}\\) data sample collected at Belle II, which operates at the SuperKEKB \\(e^+e^-\\) collider, we observe no evidence for a signal. We set upper limits on the product of the production cross section \\(\\sigma\\left(e^+e^- \\to h^\\prime \\chi_1 \\chi_2\\right)\\), and the product of branching fractions \\(\\mathcal{B}\\left(\\chi_2\\to\\chi_1 e^+ e^-\\right)\\times\\mathcal{B}\\left(h^\\prime\\to x^+x^-\\right)\\), where \\(x^+x^-\\) indicates \\(\\mu^+\\mu^-, \\pi^+\\pi^-\\), or \\(K^+K^-\\), as functions of \\(h^{\\prime}\\) mass and lifetime at the level of \\(10^{-1}\\,\\mbox{fb}\\). We set model-dependent upper limits on the dark Higgs mixing angle at the level of \\(10^{-5}\\) and on the dark photon kinetic mixing parameter at the level of \\(10^{-3}\\). This is the first search for dark Higgs bosons in association with inelastic dark matter.

The projected sensitivity of the effective electron neutrino-mass measurement with the KATRIN experiment is below 0.3 eV (90 % CL) after five years of data acquisition. The sensitivity is affected by the increased rate of the background electrons from KATRIN's main spectrometer. A special shifted-analysing-plane (SAP) configuration was developed to reduce this background by a factor of two. The complex layout of electromagnetic fields in the SAP configuration requires a robust method of estimating these fields. We present in this paper a dedicated calibration measurement of the fields using conversion electrons of gaseous \\(^\\mathrm{83m}\\)Kr, which enables the neutrino-mass measurements in the SAP configuration.