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Searches for exotic decays of the 125 GeV Higgs boson in the CMS experiment
No full textSince the discovery of the Higgs boson in 2012, the LHC experiments have successfully measured some of its properties with remarkable precision. However, the current integrated luminosity remains a limiting factor in probing Higgs boson self-couplings and first-generation Yukawa couplings. The current constraints on the Higgs boson couplings still allow for the possibility of a sizeable branching fraction into undetected final states. This motivates the ongoing efforts to search for exotic decay modes of the Higgs boson directly. This presentation highlights several new results from these searches using the entire LHC Run 2 data set collected by the CMS experiment
Machine Learning Inference in Athena with ONNXRuntime
No full textMachine Learning (ML)-based algorithms play increasingly important roles in almost all aspects of data processing in the ATLAS experiment at CERN. Diverse ML models are used in detector simulation, event reconstruction, and data analysis. They are being deployed in the ATLAS software framework, Athena. Our primary approach to perform ML inference in Athena is to use ONNXRuntime. ONNXRuntime is a cross-platform ML model acceleration library, with a flexible interface to integrate hardware-specific libraries. In this talk, we will describe the ONNXRuntime interface in Athena and the impact of advanced ONNXRuntime settings on various ML models and workflows at ATLAS
Beam test results of a fully 3D-printed plastic scintillator particle detector prototype
No full textPlastic scintillators are widely used for the detection ofelementary particles, and 3D reconstruction of particle tracks isachieved by segmenting the detector into 3D granular structures. Inthis study, we present a novel prototype fabricated by additivemanufacturing, consisting of a 5 × 5 × 5 array of1 cm^3 plastic scintillator cubes, each optically isolated. Thisinnovative approach eliminates the need to construct complexmonolithic geometries in a single operation and gets rid of thetraditional time-consuming manufacturing and assembling processes.The prototype underwent performance characterization during a beamtest at CERN's Proton-Synchrotron facility. Light yield, opticalcrosstalk, and light response uniformity, were evaluated. Theprototype demonstrated a consistent light yield (LY) ofapproximately 27 photoelectrons (p.e.) per channel, similar totraditional cast scintillator detectors. Crosstalk between adjacentcubes averaged 4-5%, while LY uniformity within individual cubesexhibited about 7% variation, indicating stability andreproducibility. These results underscore the potential of the noveladditive manufacturing technique, for efficient and reliableproduction of high-granularity scintillator detectors.Plastic scintillators are widely used for the detection of elementary particles, and 3D reconstruction of particle tracks is achieved by segmenting the detector into 3D granular structures. In this study, we present a novel prototype fabricated by additive manufacturing, consisting of a 5 x 5 x 5 array of 1 cm3 plastic scintillator cubes, each optically isolated. This innovative approach eliminates the need to construct complex monolithic geometries in a single operation and gets rid of the traditional time-consuming manufacturing and assembling processes. The prototype underwent performance characterization during a beam test at CERN's Proton-Synchrotron facility. Light yield, optical crosstalk, and light response uniformity, were evaluated. The prototype demonstrated a consistent light yield of approximately 27 photoelectrons (p.e.) per channel, similar to traditional cast scintillator detectors. Crosstalk between adjacent cubes averaged 4-5%, and light yield uniformity within individual cubes exhibited about 7% variation, indicating stability and reproducibility. These results underscore the potential of the novel additive manufacturing technique, for efficient and reliable production of high-granularity scintillator detectors
Observation of a new charmed baryon decaying to
No full textThe spectrum is investigated using proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb, collected by the LHCb experiment during 2016-2018. Four states are observed with high significance, and their masses and widths are measured to be \begin{equation*} m[\Xi_c(2815)^{+}] = 2816.65 \pm 0.03 \pm 0.03 \pm 0.23~\text{MeV}, \newline \Gamma[\Xi_c(2815)^{+}] = 2.07 \pm 0.08 \pm 0.12~\text{MeV}, \newline m[\Xi_c(2923)^{+}] = 2922.8 \pm 0.3 \pm 0.5 \pm 0.2~\text{MeV}, \newline \Gamma[\Xi_c(2923)^{+}] = 5.3 \pm 0.9 \pm 1.4~\text{MeV}, \newline m[\Xi_c(2970)^{+}] = 2968.6 \pm 0.5 \pm 0.5 \pm 0.2~\text{MeV}, \newline \Gamma[\Xi_c(2970)^{+}] = 31.7 \pm 1.7 \pm 1.9~\text{MeV}, \newline m[\Xi_c(3080)^{+}] = 3076.8 \pm 0.7 \pm 1.3 \pm 0.2~\text{MeV}, \newline \Gamma[\Xi_c(3080)^{+}] = 6.8 \pm 2.3 \pm 0.9~\text{MeV}, \end{equation*} \newline where the uncertainties are statistical, systematic, and due to the limited precision on the mass, respectively. The baryon is observed for the first time, and is consistent with being the isospin partner of the previously observed state. Most of the measured parameters are more precise than existing world averages.The spectrum is investigated using proton-proton collisions at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.4fb, collected by the LHCb experiment during 2016--2018. Four states are observed with high significance, and their masses and widths are measured to be \begin{align*}
m[\Xi_c(2815)^{+}] &= 2816.65 \pm 0.03 \pm 0.03 \pm 0.23 ~\text{MeV},\\
\Gamma[\Xi_c(2815)^{+}] &= 2.07 \pm 0.08 \pm 0.12~\text{MeV},\\[5pt]
m[\Xi_c(2923)^{+}] &= 2922.8 \pm 0.3 \pm 0.5 \pm 0.2~\text{MeV},\\
\Gamma[\Xi_c(2923)^{+}] &= 5.3 \pm 0.9 \pm 1.4~\text{MeV},\\[5pt]
m[\Xi_c(2970)^{+}] &= 2968.6 \pm 0.5 \pm 0.5 \pm 0.2~\text{MeV},\\
\Gamma[\Xi_c(2970)^{+}] &= 31.7 \pm 1.7 \pm 1.9~\text{MeV},\\[5pt]
m[\Xi_c(3080)^{+}] &= 3076.8 \pm 0.7 \pm 1.3 \pm 0.2~\text{MeV},\\
\Gamma[\Xi_c(3080)^{+}] &= 6.8 \pm 2.3 \pm 0.9~\text{MeV}.
\end{align*}
where the uncertainties are statistical, systematic, and due to the limited precision on the mass, respectively. The baryon is observed for the first time, and is consistent with being the isospin partner of the previously observed state. Most of the measured parameters are more precise than existing world averages
Impact of RNTuple on Storage Resources for ATLAS Production
No full textOver the past years, the ROOT team has been developing a new I/O format called RNTuple to store data from experiments at CERN's Large Hadron Collider. RNTuple is designed to improve ROOT's existing TTree I/O subsystem by improving I/O speed and introducing a more efficient binary data format. It can be stored in both ROOT files and object stores, and it's optimized for modern storage hardware like NVMe SSDs. The ATLAS experiment plans to use RNTuple as its primary storage container in the upcoming HL-LHC. There's been significant progress in integrating RNTuple into the ATLAS event processing framework, and now all production ATLAS data output formats support it. Performance studies with open-source data have shown substantial improvements in space resource usage. The reported study examines the I/O throughput and disk-space savings achieved with RNTuple for various ATLAS data output formats, including RDO, ESD, AOD, and various DAOD. These measurements will have an important impact on the computing resource needs of the ATLAS experiment for HL-LHC operatio
Detection efficiency and spatial resolution of Monolithic Active Pixel Sensors bent to different radii
No full textBent monolithic active pixel sensors are the basis for the planned fully cylindrical ultra low material budget tracking detector ITS3 of the ALICE experiment. This paper presents results from testbeam campaigns using high-energy particles to verify the performance of 50 um thick bent ALPIDE chips in terms of efficiency and spatial resolution. The sensors were bent to radii of 18, 24 and 30 mm, slightly smaller than the foreseen bending radii of the future ALICE ITS3 layers. An efficiency larger than and a spatial resolution of approximately 5 um, in line with the nominal operation of flat ALPIDE sensors, is obtained at nominal operating conditions. These values are found to be independent of the bending radius and thus constitute an additional milestone in the demonstration of the feasibility of the planned ITS3 detector. In addition, a special geometry in which the beam particles graze the chip and traverse it laterally over distances of up to 3 mm is investigated
(Re)interpretation of the LHC results for new physics
No full textColliderBit is the GAMBIT module responsible for simulating LHC physics in the GAMBIT global fitting tool. In this talk we will present recent technical developments in ColliderBit, including new LHC analysis implemented, improvements to three-body decay kinematics relevant for supersymmetry searches, as well as updates to interfaces to other codes
CMS Outer Tracker Module Production and Integration at NISER
No full textIn the LHC long shutdown 3, due to start in mid-2026, the LHC will be upgraded to the High-Luminosity LHC. To address the challenges for operation at the HL-LHC, such as an increased interaction rate and higher radiation levels, an upgrade of the tracking system of the CMS detector is being built. The new CMS Outer Tracker will feature silicon-based detector modules with on-module track-stub selection based on transverse momentum. At NISER, India, efforts focus on assembling 2S modules with two silicon strip sensors and about four thousand readout channels. Each module integrates radiation-hard ASICs, high-speed optical transmitters, and DCDC converters. After assembly, every module undergoes thorough electronic noise characterisation at C and C. Once characterised, modules are integrated into larger structures called ladders, where additional readout tests and temperature cycling validate durability before shipment to CERN. This multi-stage assembly process follows stringent quality control measures and relies on state-of-the-art machinery, including precision glue dispensers, optical metrology, and ultrasonic wire bonders. These efforts are evidence of NISER's strong commitment to the success of the HL-LHC project
Delivery of the second US-AUP cryo-assembly for the HL-LHC project at CERN
No full textThe second Q1/Q3 cryo-assembly manufactured by the HL-LHC United States Accelerator Upgrade Program (US-AUP) arrived at CERN on 8th January 2025 after a long journey from Fermilab in Batavia, Illinois. This cryo-assembly is now under incoming inspection and will then go to the second phase of cryostat assembly, before installation in the IT String in April
