Search for the Higgs boson decay to a ZZ boson and a photon in pppp collisions at s=13\sqrt{s} = 13 TeV and 13.613.6 TeV with the ATLAS detector

A search for the Higgs boson decay to a $Z$ boson and a photon in the $\ell\ell\gamma$ ($\ell = e, \mu$) final state is performed using $pp$ collisions recorded with the ATLAS detector at $\sqrt{s}=13.6$ TeV during 2022--2024, corresponding to an integrated luminosity of 165 fb$^{-1}$. The signal yield, normalized to the Standard Model prediction, is measured to be $\mu=0.9^{+0.7}_{-0.6}$, compared to an expected value of $\mu=1.0\pm0.7$. This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations with respect to the background-only hypothesis. The search is combined with those of a similar search performed with 139 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collisions to provide the most stringent expected sensitivity to date to this rare decay. This results in an observed (expected) signal strength of $\mu = 1.3^{+0.6}_{-0.5}$ ($\mu = 1.0^{+0.6}_{-0.5}$), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model expectation

Visit by Dr Stephen K. Streiffer, Director, Oak Ridge National Laboratory, USA

Visit by Dr Stephen K. Streiffer, Director, Oak Ridge National Laboratory, United States of Americ

Charm production in proton--proton collisions with ALICE at the LHC and light nuclei synthesis via coalescence in heavy-ion collisions

Ultrarelativistic heavy-ion collisions in experimental facilities are conducted to investigate the dynamics of strongly interacting matter. These laboratories produce a dense soup of deconfined quarks and gluons called the quark-gluon plasma (QGP). The ALICE experiment at the LHC is dedicated to studying this exotic state of matter that probes its formation from the aftermath of heavy-ion collisions. Heavy quarks (charm and beauty) are interesting probes to examine the QGP medium. Because of their large masses, they produce at the initial stages of the collision and get to traverse the entire evolution of the medium. Their production mechanisms in proton--proton (pp) collisions are of great interest, providing stringent tests to perturbative quantum chromodynamic (pQCD) calculations. Interestingly, heavy-quark production is also correlated to event properties. Studies have shown a strong correlation between charm production and the event multiplicity in pp collision, where a significant role of multiparton interactions is suspected. The role of auto-correlation effects between charm production and multiplicity is also weighed in. Moreover, with identifiable QGP signatures in high multiplicity pp collisions, the participation of charm in collective-like effects is also worth investigating. In addition, with event shapes, charm production can be categorized into the hard and soft components that allow unfolding of the production mechanisms with event activity. This thesis outlines the studies performed in charm production via D-meson production as a function of event-multiplicity and -shapes in pp collisions at $\sqrt{s} =$ 13 TeV. $$$$ The second focus of this thesis is on light nuclei ($\mathrm{d,~^{3}H,~^{3}He}$) production in collision experiments. Light nuclei are clusters of nucleons that survive temperatures of $\mathcal{O}(100~\mathrm{MeV})$ in heavy-ion collisions, orders higher than its binding energy. Understanding their $`$puzzling' production mechanism is a contentious topic in the community, with the coalescence of nucleons being one of the popular phenomenological models. It is based on the overlap principle between the nucleon phase-space distribution and the nuclei probability distribution. The nucleon phase space generally relies upon an event generator, to which coalescence is appended in an afterburner mode. The coalescence model is initially designed with a box nuclei distribution prescription, which is studied on $\mathrm{d,~^{3}H,~^{3}He}$ production in RHIC and LHC energies. The model is revamped with the nuclei's Wigner distribution, inspired by its quantum mechanical wavefunction. With this update, finer details can be added in terms of a common nucleon emission source. This connects the nucleon-nucleon (NN) interactions during the inception of the light cluster formation in these collision experiments. Furthermore, investigation with strong, Coulombic and quantum statistical corrections will capture the femtoscopic details in these NN interactions. This thesis includes all the stages of developing an $`$in-situ' coalescence model discussed above and its implementation

AIDAinnova Course on Quantum Applications

Hybrid pixel detectors are now ubiquitous in High Energy Physics experiments. This is because they are able to provide noise hit free data with very high timestamp precision. Following pioneering work in the Medipix Collaborations, the same technology is now used in multiple other fields ranging from photon science, to space-based dosimetry, to medical imaging and more recently to quantum applications. The Timepix family of pixel detector readout ASICs was designed in response to a request for time stamping at the pixel level for an envisaged gas detector-based Time Projection Chamber. In the first version of the chip each pixel could be programmed to measure one of 3 parameters: total counts, Time over Threshold (ToT), or Time of Arrival (ToA). Readout was frame-based. Successive designs have added data driven readout and much higher time precision. This talk will introduce the Timepix family of readout chips highlighting the key features for each generation. Some of the fundamental design constraints will be discussed along with potential future avenues for development

Performance and operational experience of ALICE ITS2 in LHC Run 3

The ALICE experiment underwent major upgrades during the LHC Long Shutdown 2 (2019–2021), including the installation of the new Inner Tracking System (ITS2). ITS2 comprises seven layers with 12.5 billion pixels covering 10 m^2, based on the ALPIDE CMOS Monolithic Active Pixel Sensors (MAPS), which offer a spatial resolution of approximately 5 µm. Designed to handle Pb–Pb collisions at interaction rates of up to 50 kHz, ITS2 delivers enhanced tracking performance, particularly in terms of impact-parameter resolution and efficiency at low transverse momentum. This improvement is achieved through its increased granularity, low material budget of 0.36% X$_{0}$ per layer in the innermost layers, and the closer placement of the first layer at a radial distance of 22.4 mm from the interaction point.ITS2 became fully operational at the beginning of LHC Run 3 and has demonstrated excellent performance in both proton–proton and heavy-ion collisions. This paper presents a summary of the operational experience and performance of ITS2, with a particular focus on detector calibration and tracking performance. Lessons learned from ITS2 operation, including beam-induced background mitigation strategies, are also discussed in the context of guiding the development of next-generation tracking systems such as ITS3 and the ALICE 3 vertex detector

2025 High voltage scan studies for RPC

Results from the 2025 High voltage scan studies performed with the CMS RPC system are presented

CMS results on dark QCD signatures (emerging jets, semivisible jets, SUEP)

We present recent results from the CMS experiment on searches for strongly coupled dark sectors using data collected during LHC Run 2. Such models can give rise to unconventional final states that may evade traditional LHC searches, including jets with unusual substructure, events with high multiplicities of soft, spherically distributed particles, or multiple displaced vertices.This report focuses on the latter two scenarios. CMS conducted three complementary analyses targeting different production modes of Soft Unclustered Energy Patterns (SUEPs) arising from scalar mediators with masses between 125 and 2000 GeV. These analyses set the first limits on dark sector models predicting high-multiplicity, high-sphericity final states. Additionally, leveraging alternative data acquisition strategies such as B-parking, CMS places the most stringent constraints to date on dark sector scenarios producing dimuons displaced within the tracker volume with invariant masses as low as 0.33 GeV