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Testing and Processing of Pre-production 325 MHz Single Spoke Resonator Power Couplers for PIP-II Project
Fundamental 325 MHz power couplers are designed, built and tested for SSR cavities in PIP-II project. Couplers should work in CW mode at power level 7.5kW w/o beam and ~15 kW with the 2 mA beam. At pre-production stage we built and tested 6 couplers, produced by CPI (FNAL) and PMB (IJCLab) and 4 more couplers will be tested soon. Two of tested couplers had TiN coated ceramic window. In warm test stand two couplers were mounted on the coupling chamber and tested in SW regime at full reflection with phase controlled by position of short and reflection insert. Couplers were tested at pulse mode (up to 25kW) and cw mode (12kW) with HV bias or without bias. Test results demonstrated that 3.5 kV DC bias completely suppresses multipactor in coupler. Vacuum activity in coupler was controlled by e-pickups and build-in vacuum gauges, located near the vacuum side of window. Power processing without DC bias was done for several couplers with and without TiN coating on ceramic window. Test results are presented and discussing in paper.
TESTING AND PROCESSING OF PRE-PRODUCTION 325 MHZ SINGLE SPOKE RESONATOR POWER COUPLERS FOR PIP-II PROJECT
Fundamental 325 MHz power couplers are designed, built and tested for SSR cavities in PIP-II project [1]. Couplers should work in CW mode at power level 7.5kW w/o beam and ~15 kW with the 2 mA beam. At pre-production stage we built and tested 6 couplers, produced by CPI (FNAL) and PMB (IJCLab) and 4 more couplers will be tested soon. Two of tested couplers had TiN coated ceramic window. In warm test stand two couplers were mounted on the coupling chamber and tested in SW regime at full reflection with phase controlled by position of short and reflection insert. Couplers were tested at pulse mode (up to 25kW) and cw mode (12kW) with HV bias or without bias. Test results demonstrated that 3.5 kV DC bias completely suppresses multipactor in coupler. Vacuum activity in coupler was controlled by e-pickups and build-in vacuum gauges, located near the vacuum side of window. Power processing without DC bias was done for several couplers with and without TiN coating on ceramic window. Test results are presented and discussing in paper.
Deuteron production in AuAu collisions at s N N = 7 – 200 GeV via pion catalysis
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MicroBooNE's First Search for the MiniBooNE Anomalous Excess Under a Photon-Like Hypothesis with High-Sensitivity Search for Neutrino-Induced Neutral Current Delta Production and Radiative Decay
MicroBooNE is a liquid argon time projection chamber that collected neutrino data at Fermilab's Booster Neutrino Beam from 2015 to 2020. One of its primary goals is to investigate the “Low Energy Excess” of neutrino events observed by the MiniBooNE experiment, for which candidate photon-like interpretations include an underestimation of neutrino neutral current (NC) resonant $\Delta$ production with subsequent radiative decay or another anomalous source of single photon production in neutrino interactions. In particular, NC $\Delta$ radiative decay is poorly constrained background process to electron neutrino measurements and could be a sizable contribution to the “Low Energy Excess.” This thesis will present the analysis developed to search for NC $\Delta \rightarrow N\gamma$ events in MicroBooNE, consisting of a boosted decision tree based event selection with an NC neutral pion background constraint, using data from the first three years of operations corresponding to $6.9\times10^{20}$ POT.
Deuteron production in relativistic heavy ion collisions via stochastic multiparticle reactions
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Probing Parton Saturation and the Gluon Dipole via Diffractive Jet Production at the Electron-Ion Collider
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Bottomonium production in heavy-ion collisions using quantum trajectories: Differential observables and momentum anisotropy
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Axion-like particle searches at DarkQuest
Axion-like particles (ALPs) interacting with the Standard Model can be abundantly produced in proton beam fixed-target experiments. Looking for their displaced decays is therefore an effective search strategy for ALPs with a mass in the MeV to GeV range. Focusing on the benchmark models where the ALP interacts dominantly with photons or gluons, we show that the proposed DarkQuest experiment at Fermilab will be able to test parameter space which has been previously inaccessible. We pay particular attention to the self-consistency of gluon-coupled ALP production and decay calculations, which has been recently shown to be a problem in many existing predictions. We also apply these results to explore existing constraints in the ALP parameter space.
Shower Reconstruction for Cross-Section Measurements with Photon(s) in the Final State at SBND
The Short-Baseline Near Detector (SBND) is a 112-ton liquid argon time projection chamber operating in the Booster Neutrino Beam at Fermilab as part of the Short-Baseline Neutrino Program. Precise reconstruction of electromagnetic showers from photons and electrons is essential for searches for neutrino oscillations, cross-section measurements, and rare-process studies in liquid argon. In this poster, we present a unified set of SBND analyses enabled by the SPINE (Scalable Particle Imaging with Neural Embeddings) end-to-end machine-learning–based reconstruction framework, highlighting charged-current neutral pion (CC π⁰) production and neutral-current (NC) Δ radiative decay as complementary physics cases. Charged-current π⁰ interactions provide a high-statistics benchmark for validating photon reconstruction, constraining the electromagnetic energy scale, and modeling backgrounds to other cross-section measurements and BSM searches with one or more photons in the final state. We summarize progress toward the ongoing development of a CC π⁰ selection in SBND and, report on the current status of a search for NC resonant Δ production followed by radiative decay (Δ→Nγ) in SBND. This rare process, previously investigated in MicroBooNE, provides a stringent test of photon-only final-state reconstruction and is of interest in the context of the MiniBooNE low-energy excess. Together, these analyses demonstrate how modern machine-learning–based shower reconstruction enables a diverse and scalable physics program at SBND.
Measurement of the $\Upsilon$(1S) pair production cross section and search for resonances decaying to $\Upsilon$(1S)$\mu^+\mu^-$ in proton-proton collisions at $\sqrt{s} =$ 13 TeV
The fiducial cross section for Y(1S) pair production in proton-proton collisions at a center-of-mass energy of 13 TeV in the region where both Y(1S) mesons have an absolute rapidity below 2.0 is measured to be 79±11(stat)±6(syst)±3(B) pb assuming the mesons are produced unpolarized. The last uncertainty corresponds to the uncertainty in the Y(1S) meson dimuon branching fraction. The measurement is performed in the final state with four muons using proton-proton collision data collected in 2016 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb−1 . This process serves as a standard model reference in a search for narrow resonances decaying to Y(1S)μ+μ− in the same final state. Such a resonance could indicate the existence of a tetraquark that is a bound state of two b quarks and two b¯ antiquarks. The tetraquark search is performed for masses in the vicinity of four times the bottom quark mass, between 17.5 and 19.5 GeV, while a generic search for other resonances is performed for masses between 16.5 and 27 GeV. No significant excess of events compatible with a narrow resonance is observed in the data. Limits on the production cross section times branching fraction to four muons via an intermediate Y(1S) resonance are set as a function of the resonance mass.
Photonuclear tomography in ultraperipheral heavy-ion collisions
We present a theoretical investigation of photonuclear tomography as a novel technique for probing the internal structure of nuclei. In this approach, ultraperipheral heavy-ion collisions (UPCs) serve as a source of intense fluxes of virtual photons, which induce coherent production of vector mesons. By analyzing the probabilities and cross sections of these photon-induced processes, we propose a methodology for reconstructing the spatial distribution of nucleons within the nucleus. Our framework provides a systematic way to access information on the nuclear geometry probed in UPCs, offering new opportunities for studies of nuclear structure using particle production as a probe. Numerical calculations for selected examples illustrate the feasibility and potential of this method.
Differential two-particle number and momentum correlations with the AMPT, UrQMD, and EPOS models in Pb-Pb collisions at s N N = 2.76 TeV
We report studies of charge-independent and charge-dependent two-particle differential number correlation functions, R 2 (Δη,Δφ), and transverse momentum correlation functions, P 2 (Δη,Δφ), of charged particles produced in Pb–Pb collisions at the LHC center-of-mass energy √sNN= 2.76 TeV with the UrQMD, AMPT, and EPOS models. Model calculations for R2 and P2 correlation functions are presented for inclusive charged hadrons (h ± ) in selected transverse momentum ranges and with full azimuthal coverage in the pseudorapidity range |η|<1.0. We compare these calculations for the strength, shape, and particularly the width of the correlation functions with recent measurements of these observables by the ALICE collaboration. Our analysis indicates that comparative studies of R 2 and P 2 correlation functions provide valuable insight towards the understanding of particle production in Pb–Pb collisions. We find, in particular, that these models produce quantitatively different magnitudes and shapes for these correlation functions and none reproduce the results reported by the ALICE collaboration. Accounting for quantum number conservation in models, particularly charge conservation, is mandatory to reproduce the detailed measurements of number and transverse momentum correlation functions.
FACET: a new long-lived particle detector in the very forward region of the CMS experiment
We describe a proposal to add a set of very forward detectors to the CMS experiment for the high-luminosity era of the Large Hadron Collider to search for beyond the standard model long-lived particles, such as dark photons, heavy neutral leptons, axion-like particles, and dark Higgs bosons. The proposed subsystem is called FACET for Forward-Aperture CMS ExTension, and will be sensitive to any particles that can penetrate at least 50 m of magnetized iron and decay in an 18 m long, 1 m diameter vacuum pipe. The decay products will be measured in detectors using identical technology to the planned CMS Phase-2 upgrade.
High-dimensional anomaly detection with radiative return in $\mathcal{e}$⁺$\mathcal{e}$⁻ collisions
Experiments at a future $\mathcal{e}$⁺$\mathcal{e}$⁻ collider will be able to search for new particles with masses below the nominal centre-of-mass energy by analyzing collisions with initial-state radiation (radiative return). We show that machine learning methods that use imperfect or missing training labels can achieve sensitivity to generic new particle production in radiative return events. In addition to presenting an application of the classification without labels (CWoLa) search method in $\mathcal{e}$⁺$\mathcal{e}$⁻ collisions, our study combines weak supervision with variable-dimensional information by deploying a deep sets neural network architecture. We have also investigated some of the experimental aspects of anomaly detection in radiative return events and discuss these in the context of future detector design.
Role of bulk viscosity in deuteron production in ultrarelativistic nuclear collisions
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Light nuclei production in a multiphase transport model for relativistic heavy ion collisions
Based on an enhanced multiphase transport (AMPT) model, which gives a good description of proton production with a smooth quark matter to hadronic matter transition in relativistic heavy ion collisions, we study deuteron and triton productions from the coalescence of nucleons at the kinetic freezeout of these collisions. For central Au + Au collisions at center-of-mass energies √s NN from 7.7 GeV to 200 GeV available at the Relativistic Heavy Ion Collider (RHIC), we find that the yield ratio N t N p /N$^2_d$ of proton, deuteron, and triton is a monotonic function of collision energy. Our study confirms the results from similar studies based on different dynamic model, which have either no phase transition or a crossover transition between the quark-gluon plasma and the hadronic matter, that this yield ratio does not show any nonmonotonic behavior in its collision-energy dependence.
Enhanced production of strange baryons in high-energy nuclear collisions from a multiphase transport model
Here, we introduce additional coalescence factors for the production of strange baryons in a multiphase transport (AMPT) model in order to describe the enhanced production of multistrange hadrons observed in Pb + Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV at the Large Hadron Collider (LHC) and Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV at Relativistic Heavy-Ion Collider (RHIC). This extended AMPT model is found to also give a reasonable description of the multiplicity dependence of the strangeness enhancement observed in high multiplicity events in $\textit{pp}$ collisions at $\sqrt{s}$ = 7 TeV and $\textit{p}$-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. We find that the coalescence factors depend on the system size but not much on whether the system is produced from A + A or $\textit{p}$ + A collisions. Here, the extended AMPT model thus provides a convenient way to model the mechanism underlying the observed strangeness enhancement in collisions of both small and large systems at RHIC and LHC energies.