The H1 Collaboration reports the first measurement of the 1-jettiness event shape observable \(\tau_1^b\) in neutral-current deep-inelastic electron-proton scattering (DIS). The observable ...\(\tau_1^b\) is equivalent to a thrust observable defined in the Breit frame. The data sample was collected at the HERA \(ep\) collider in the years 2003-2007 with center-of-mass energy of \(\sqrt{s}=319\,\text{GeV}\), corresponding to an integrated luminosity of \(351.1\,\text{pb}^{-1}\). Triple differential cross sections are provided as a function of \(\tau_1^b\), event virtuality \(Q^2\), and inelasticity \(y\), in the kinematic region \(Q^2>150\,\text{GeV}^{2}\). Single differential cross section are provided as a function of \(\tau_1^b\) in a limited kinematic range. Double differential cross sections are measured, in contrast, integrated over \(\tau_1^b\) and represent the inclusive neutral-current DIS cross section measured as a function of \(Q^2\) and \(y\). The data are compared to a variety of predictions and include classical and modern Monte Carlo event generators, predictions in fixed-order perturbative QCD where calculations up to \(\mathcal{O}(\alpha_s^3)\) are available for \(\tau_1^b\) or inclusive DIS, and resummed predictions at next-to-leading logarithmic accuracy matched to fixed order predictions at \(\mathcal{O}(\alpha_s^2)\). These comparisons reveal sensitivity of the 1-jettiness observable to QCD parton shower and resummation effects, as well as the modeling of hadronization and fragmentation. Within their range of validity, the fixed-order predictions provide a good description of the data. Monte Carlo event generators are predictive over the full measured range and hence their underlying models and parameters can be constrained by comparing to the presented data.
The H1 Collaboration at HERA reports the first measurement of groomed event shape observables in deep inelastic electron-proton scattering (DIS) at \(\sqrt{s}=319\) GeV, using data recorded between ...the years 2003 and 2007 with an integrated luminosity of \(351\) pb\(^{-1}\). Event shapes provide incisive probes of perturbative and non-perturbative QCD. Grooming techniques have been used for jet measurements in hadronic collisions; this paper presents the first application of grooming to DIS data. The analysis is carried out in the Breit frame, utilizing the novel Centauro jet clustering algorithm that is designed for DIS event topologies. Events are required to have squared momentum-transfer \(Q^2 > 150\) GeV\(^2\) and inelasticity \( 0.2 < y < 0.7\). We report measurements of the production cross section of groomed event 1-jettiness and groomed invariant mass for several choices of grooming parameter. Monte Carlo model calculations and analytic calculations based on Soft Collinear Effective Theory are compared to the measurements.
The Breit frame provides a natural frame to analyze lepton-proton scattering events. In this reference frame, the parton model hard interactions between a quark and an exchanged boson defines the ...coordinate system such that the struck quark is back-scattered along the virtual photon momentum direction. In Quantum Chromodynamics (QCD), higher order perturbative or non-perturbative effects can change this picture drastically. As Bjorken-\(x\) decreases below one half, a rather peculiar event signature is predicted with increasing probability, where no radiation is present in one of the two Breit-frame hemispheres and all emissions are to be found in the other hemisphere. At higher orders in \(\alpha_s\) or in the presence of soft QCD effects, predictions of the rate of these events are far from trivial, and that motivates measurements with real data. We report on the first observation of the empty current hemisphere events in electron-proton collisions at the HERA collider using data recorded with the H1 detector at a center-of-mass energy of 319 GeV. The fraction of inclusive neutral-current DIS events with an empty hemisphere is found to be \(0.0112 \pm 3.9\,\%_\text{stat} \pm 4.5\,\%_\text{syst} \pm 1.6\,\%_\text{mod}\) in the selected kinematic region of \(150< Q^2<1500\) GeV\(^2\) and inelasticity \(0.14< y<0.7\). The data sample corresponds to an integrated luminosity of 351.1 pb\(^{-1}\), sufficient to enable differential cross section measurements of these events. The results show an enhanced discriminating power at lower Bjorken-\(x\) among different Monte Carlo event generator predictions.
The Electron-Ion Collider (EIC), a state-of-the-art facility for studying the strong force, is expected to begin commissioning its first experiments in 2028. This is an opportune time for artificial ...intelligence (AI) to be included from the start at this facility and in all phases that lead up to the experiments. The second annual workshop organized by the AI4EIC working group, which recently took place, centered on exploring all current and prospective application areas of AI for the EIC. This workshop is not only beneficial for the EIC, but also provides valuable insights for the newly established ePIC collaboration at EIC. This paper summarizes the different activities and R&D projects covered across the sessions of the workshop and provides an overview of the goals, approaches and strategies regarding AI/ML in the EIC community, as well as cutting-edge techniques currently studied in other experiments.
PLB 844 (2023) 138101 The radiation pattern within high energy quark- and gluon-initiated jets (jet
substructure) is used extensively as a precision probe of the strong force as
well as an ...environment for optimizing event generators with numerous
applications in high energy particle and nuclear physics. Looking at
electron-proton collisions is of particular interest as many of the
complications present at hadron colliders are absent. A detailed study of
modern jet substructure observables, jet angularities, in electron-proton
collisions is presented using data recorded using the H1 detector at HERA. The
measurement is unbinned and multi-dimensional, using machine learning to
correct for detector effects. All of the available reconstructed object
information of the respective jets is interpreted by a graph neural network,
achieving superior precision on a selected set of jet angularities. Training
these networks was enabled by the use of a large number of GPUs in the
Perlmutter supercomputer at Berkeley Lab. The particle jets are reconstructed
in the laboratory frame, using the $k_{\mathrm{T}}$ jet clustering algorithm.
Results are reported at high transverse momentum transfer $Q^2>150$ GeV^2$,
and inelasticity $0.2 < y < 0.7$. The analysis is also performed in sub-regions
of $Q^2$, thus probing scale dependencies of the substructure variables. The
data are compared with a variety of predictions and point towards possible
improvements of such models.
Cerenkov technology is often the optimal choice for particle identification in high energy particle collision applications. Typically, the most challenging regime is at high pseudorapidity (forward) ...where particle identification must perform well at high high laboratory momenta. For the upcoming Electron Ion Collider (EIC), the physics goals require hadron (\(\pi\), K, p) identification up to \(\sim\)~50 GeV/c. In this region Cerenkov Ring-Imaging is the most viable solution.\newline The speed of light in a radiator medium is inversely proportional to the refractive index. Hence, for PID reaching out to high momenta a small index of refraction is required. Unfortunately, the lowest indices of refraction also result in the lowest light yield (\(\frac{dN_\gamma}{dx} \propto \sin^2{\left(\theta_C \right)}\)) driving up the radiator length and thereby the overall detector cost. In this paper we report on a successful test of a compact RICH detector (1 meter radiator) capable of delivering in excess of 10 photoelectrons per ring with a low index radiator gas (\(CF_4\)). The detector concept is a natural extension of the PHENIX HBD detector achieved by adding focusing capability at low wavelength and adequate gain for high efficiency detection of single-electron induced avalanches. Our results indicate that this technology is indeed a viable choice in the forward direction of the EIC. The setup and results are described within.
