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Measurement of event shapes in minimum-bias events from proton-proton collisions at = 13 TeV
No full textA measurement of event-shape variables is presented, using a data sample produced in a special run with approximately one inelastic proton-proton collision per bunch crossing. The data were collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 64 b. A number of observables related to the overall distribution of charged particles in the collisions are corrected for detector effects and compared with simulations. Inclusive event-shape distributions, as well as differential distributions of event shapes as functions of charged-particle multiplicity, are studied. None of the models investigated is able to satisfactorily describe the data. Moreover, there are significant features common amongst all generator setups studied, particularly showing data being more isotropic than any of the simulations. Multidimensional unfolded distributions are provided, along with their correlations
Performance and efficiency of a transformer-based quark/gluon jet tagger in the ATLAS experiment
No full textA deep-learning approach based on the transformer architecture is developed to distinguish between jets originating from quarks and gluons. The algorithm operates on jets with transverse momentum and pseudorapidity and takes as input several properties derived from the jet constituents, using information from the ATLAS detector's tracker and calorimeter. The algorithm's performance is evaluated by analyzing dijet data events from proton-proton collisions at and TeV during Run 2 and Run 3 of the Large Hadron Collider. Two methods are used to obtain distributions from quark- or gluon-initiated jets in data: a matrix method fully based on Monte Carlo simulation and a new approach named `jet topics' which has less dependence on the modelling of the physics process under study. The quark and gluon identification efficiencies measured in data for the 50% quark-identification-efficiency working point vary from the simulated ones for quark-initiated (gluon-initiated) jets by factors of 0.88-1.30 (0.61-1.05) with uncertainties of 10%-70% (10%-95%). The uncertainties estimated with the jet topics method are smaller than those estimated with the matrix method, with up to 20% less systematic uncertainty in some phase-space regions. The advances in jet identification reported here provide a robust tool for precision Standard Model measurements and searches for new physics at the LHC
PETRA-IV FOFB System Integration Test Setup
No full textThe PETRA-IV Fast Orbit Feedback (FOFB) system will be a large-scale Multi-Input Multi-Output (MIMO) control system, utilizing 790 Beam Position Monitors (BPM) and 560 Fast Corrector Magnets (FCM) to maintain the desired orbit trajectory. Data acquisition and distribution will be managed across 16 supply areas and connected via an extended star network topology. This contribution focuses on system integration test setups while describing the Model-Based Design (MBD) methodologies that are being used for developing, verifying, and commissioning the complete system step by step. Integration of the components of such a large system must be systematic so that potential issues can be isolated and fixed efficiently. The setups will also be used for the characterization of sensors, actuators, and transmission lines. Subsystem identification is of utmost importance for a comprehensive understanding of the system dynamics, which will guide the design of appropriate filters and control strategies to ensure optimal orbit stabilization performance. The analysis will also precisely assess the overall system latency, which is critical for feedback bandwidth and stability
Two-loop helicity amplitudes for diphoton production with massive quark loop
No full textWe compute two-loop helicity amplitudes in QCD for diphoton production through quark- and gluon-initiated channels, accounting for a massive internal quark loop by keeping its full mass dependence. Using physical projectors, we directly decompose the amplitude into its helicity components. By renormalising the heavy quark mass in on-shell, and other quantities in schemes, we obtain finite remainders. This work paves the way for calculating the cross-section for diphoton production at higher orders in QCD with a massive quark loop, employing different subtraction schemes. The effect of a heavy quark is expected to play a crucial role in high-luminosity LHC
Theory uncertainties in the extraction of α from Drell-Yan at small transverse momentum
No full textWe perform a detailed pseudodata study to estimate the expected theory uncertainty in the extraction of the strong coupling constant, α(m), from a fit to the measured Drell-Yan transverse momentum (q) spectrum at small q ≪ m. We consider two approaches to estimate the dominant perturbative uncertainties. We first discuss that the traditional approach based on varying unphysical scales is insufficient here because it cannot correctly account for bin-by-bin theory correlations in the q spectrum, which are critically important in this case. We then use this case as a nontrivial application of a new approach based on theory nuisance parameters (TNPs), which encodes the correct theory correlations by construction. Moreover, the TNPs can be profiled in the fit thereby allowing the data to constrain the theory uncertainties in a consistent manner. We furthermore discuss the interplay with nonperturbative effects in the peak region q ≲ 10 GeV, from where most of the α sensitivity originates. The associated nonperturbative uncertainties on α when fitting only the q spectrum are large. They can in principle be reduced by including additional constraints on the nonperturbative Collins-Soper kernel from lattice QCD calculations. We find that these improvements in the treatment of perturbative and nonperturbative uncertainties and their correlations will enable a competitive α extraction from Drell-Yan data at small q. We also discuss the implications of our findings, calling into question a recent α extraction from the Z q spectrum by the ATLAS experiment
Sparsity in the numerical six-point bootstrap
No full textThe paper contributes to an ongoing effort to extend the conformal bootstrap beyond its traditional focus on systems of four-point correlation functions. Recently, it was demonstrated that semidefinite programming can be used to formulate a six-point generalisation of the numerical bootstrap, yielding qualitatively new, rigorous bounds on CFT data. However, the numerical six-point bootstrap requires solving SDPs involving infinite-dimensional matrices, which has so far limited its applicability and hindered scalability in early implementations. This work overcomes the challenges by using sparse matrix decompositions to exploit the banded structure of the underlying SDP. The result is a rewriting of one-dimensional six-point bootstrap problems as effectively two-dimensional standard mixed correlator four-point bootstrap computations. As application, novel bounds whose extremal correlators interpolate between the six-point functions of the generalised free fermion and boson are derived. The extremal interpolations are matched with perturbative deformations of the massive free boson in AdS
Realizing string breaking dynamics in a lattice gauge theory on quantum hardware
No full textWe investigate static and dynamical aspects of string breaking in a lattice gauge theory coupled to Kogut-Susskind staggered fermions. Using tensor network simulations, we demonstrate that the static potential as well as the site-resolved configuration of the matter sites and gauge links allows us to identify the regimes in which string breaking occurs. Furthermore, we develop a variational quantum eigensolver that allows for reliably preparing the ground state of the theory in both the absence and presence of static charges and to capture the static aspects of the phenomenon. Carrying out state preparation on real quantum hardware for up to 19 qubits, we demonstrate its suitability for current quantum devices. In addition, we study the real-time dynamics of a flux tube between two static charges using both tensor networks and quantum hardware. Using a trotterization for the time-evolution operator, we are able to show that the breaking process starts with the creation of charges inside the string. These eventually redistribute toward the static charges and screen them, which leads to the breaking of the flux tube
A Journey through Applied Mathematics, Experimental Physics, Beamline Simulations, and FAIR data
No full textAcademic Talk for the Young Crystallographers Meeting in October 2025 at BESSY synchrotron in Berlin, Germany. The talk covers academic research, but focuses also on challenges and solutions in academic careers