Physics

International MasterClasses (IMC), an outreach activity of the International Particle Physics Outreach Group (IPPOG), has been bringing cutting-edge particle physics research to schoolchildren for over 15 years now. All four LHC experiments participate in the event, including ALICE, the experiment optimised for the study of heavy-ion collisions. Heavy-ion physics is actively contributing to IMC with new developments including experimental measurements but also applications for society, such as treatment of cancer with ions. In particular, ALICE provides three MC measurements related to the main observables used to characterize the properties of the produced Quark-Gluon Plasma. Historically, those MC measurements were developed independently, inheriting from the first one, by several ALICE groups. Since all of them are based on the ROOT EVE package, a project to integrate them into a common framework was undertaken. ALICE delivers now a single and easy-to-use application, compiled under Linux, MacOS, and, for the first time, Windows. Then, in line with current IPPOG goals to increase the global reach and scope of the IMC programme a newly developed measurement on medical applications of particle physics, the Particle Therapy MasterClass (PTMC) was introduced in the IMC2020 programme. It is a simplified version of matRad, a MATLAB-based toolkit for calculation of dose deposition in the body and allows for planning of radiotherapy using different modalities and highlighting the benefits of treatment with ions.

To measure oscillation of a simple pendulum was probably a first idea coming to mind after appearance of smartphones with small but powerful acceleration sensors~: Simply attach the telephone to a playground swing or hang it on two string as the pendulum bob and record the data. But immediately the problem becomes not so trivial. To deeply investigate on it or to make the phase diagram of the movement require complex calculations that are far beyond the capability of the youngest students. In this article we propose another way to study the pendulum by putting the sensors at the axis of rotation. This method gives immediately the figures very close to ones in textbooks.

Experimental analysis of the motion in a system of two coupled oscillators with arbitrary initial conditions was performed and the normal coordinates were obtained directly. The system consisted of two gliders moving on an air track, joined together by a spring and joined by two other springs to the fixed ends. From the positions of the center of mass and the relative distance, acquired by analysis of the digital video of the experiment, normal coordinates were obtained, and by a non linear fit the normal frequencies were also obtained. It is shown that although the masses of the springs are relatively small compared to that of the gliders, it is necessary to take them into consideration to improve the agreement with the experimental results. This experimental-theoretical proposal is targeted to an undergraduate laboratory.

An analysis of institutional data to understand the outcome of the many obstacles faced by students from historically disadvantaged backgrounds is important in order to work towards promoting equity and inclusion for all students. We use 10 years of institutional data at a large public research university to investigate the grades earned (both overall and in STEM courses only) by students categorized on four demographic characteristics: gender, race/ethnicity, low-income status, and first-generation college student status. We find that on average across all years of study and for all clusters of majors, underrepresented minority students experience a larger penalty to their mean overall and STEM GPA than even the most disadvantaged non-URM students. Moreover, the underrepresented minority students with additional disadvantages due to socioeconomic status or parental education level were even further penalized in their average GPA. Furthermore, we also find that while women in all demographic groups had a higher average overall GPA, these gender differences are almost completely non-existent in STEM GPA except among the most privileged students. These findings suggest that there is need to provide support to bridge the gaps that emanate from historical disadvantages to certain groups.

Transitions between low-lying electron states in atoms of heavy elements lead to electromagnetic radiation with discrete energies between about 0.1~keV and 100~keV (x rays) that are characteristic of the element. Moseley's law --- an empirical relation first described by Moseley in 1913 which supported predictions of the then-new Bohr model of atomic energy levels while simultaneously identifying the integer atomic number Z as the measure of nuclear charge --- predicts that the energy of these characteristic x rays scales as Z 2 . The foundational nature of Moseley's experiment has led to the popularity of Moseley's law measurements in undergraduate advanced laboratory physics courses. We report here observations of deviations from Moseley's law in the characteristic K α x-ray emission of 13 elements ranging from Z=29 to Z=92 . %: Cu, Rb, Mo, Ag, In, Ba, Tb, Ta, W, Pb, Au, Pt, and U. While following the square-law predictions of the Bohr model fairly well at low Z , the deviations become larger with increasing Z (negligible probability of the Bohr model fitting data by a χ 2 test). We find that relativistic models of atomic structure are necessary to fit the full range of atomic numbers observed (probability value of 0.20 for the relativistic Bohr-Sommerfeld model). As has been argued by previous authors, measurements of the relativistic deviations from Moseley's law are both pedagogically valuable at the advanced laboratory level and accessible with modern but modest apparatus. Here, we show that this pedagogical value can be be extended even further --- to higher Z elements, where the effects are more dramatically observable --- using apparatus which is enhanced relative to more modest versions, but nevertheless still accessible for many teaching laboratories.

Sound educational policy recommendations require valid estimates of causal effects, but observational studies in physics education research sometimes have loosely specified causal hypotheses. The connections between the observational data and the explicit or implicit causal conclusions are sometimes misstated. The link between the causal conclusions reached and the policy recommendations made is also sometimes loose. Causal graphs are used to illustrate these issues in several papers from Physical Review Physics Education Research. For example, the core causal conclusion of one paper rests entirely on the choice of a causal direction although an unstated plausible alternative gives an exactly equal fit to the data.

During the SARS-CoV-2 pandemic, theoretical high-energy physics, and likely also the majority of other disciplines, are seeing a surge of virtual seminars as a primary means for scientific exchange. In this brief article, we highlight some compelling benefits of virtualizing research talks, and argue for why virtual seminars should continue even after the pandemic. Based on our extensive experience on running online talks, we also summarize some basic guidelines on organizing virtual seminars, and suggest some directions in which they could evolve.

The number and use of research-based assessments (RBAs) has grown significantly over the last several decades. Data from RBAs can be compared against national datasets to provide instructors with empirical evidence on the efficacy of their teaching practices. Many physics instructors, however, opt not to use RBAs due to barriers such as having to use class time to administer them. In this article we examine how these barriers can be mitigated through online administrations of RBAs, particularly through the use of free online RBA platforms that automate administering, scoring, and analyzing RBAs (e.g., the Learning About STEM Student Outcomes [LASSO], Colorado Learning Attitudes About Science Survey for Experimental Physics [E-CLASS], Physics Lab Inventory of Critical thinking [PLIC], and PhysPort DataExplorer platforms). We also explore the research into common concerns of administering RBAs online and conclude with a practical how-to guide for instructors.

Social distancing due to the Covid-19 pandemic deeply impacted on education worldwide, since schools and universities had to rapidly organise lessons and courses on line. Traditional interactions between teachers and students and, also among students, had to change and was substituted by on line connections. In this context, laboratory work and tutoring, which have an important role in the peer instruction model, needed to be redesigned. Here, we discuss an on line tutoring model adopted for the introductory physics courses at Turin Polytechinc University and evaluate its effectiveness by analysing the students performance both during the semester and the summer and autumn exam sessions.

We are developing a new research based assessment (RBA) focused on quantitative reasoning -- rather than conceptual understanding -- in physics contexts. We rapidly moved administration of the RBA online in Spring 2020 due to the COVID-19 pandemic. We present our experiences with online, unproctored administration of an RBA in development to students enrolled in a large-enrollment, calculus-based, introductory physics course. We describe our attempts to adhere to best practices on a limited time frame, and present a preliminary analysis of the results, comparing results from the online administration to earlier results from in-person, proctored administration. We include discussion of online administration of multiple-choice/multiple-response (MCMR) items, which we use on the instrument as a way to probe multiple facets of student reasoning. Our initial comparison indicates little difference between online and paper administrations of the RBA, consistent with previous work by other researchers.