Challenges for FCC-ee luminosity monitor design

For cross section measurements, an accurate knowledge of the integrated luminosity is required. The FCC-ee physics programme at and around the Z pole sets the ambitious precision goal of $$10^{-4}$$ 10 - 4 on the absolute luminosity measurement and one order of magnitude better on the relative measurement between energy scan points. The luminosity is determined from the rate of Bhabha scattering, $$\mathrm {e^+e^- \rightarrow e^+e^-}$$ e + e - → e + e - , where the final state electrons and positrons are detected in dedicated monitors covering small angles from the outgoing beam directions. The constraints on the luminosity monitors are multiple: (i) they are placed inside the main detector volume only about 1 m from the interaction point; (ii) they are centred around the outgoing beam directions and do not satisfy the normal axial detector symmetry; (iii) their coverage is limited by the beam pipe, on the one hand, and by the requirement to stay clear of the main detector acceptance, on the other; (iv) the steep angular dependence of the Bhabha scattering process imposes a precision on the acceptance limits at about 1 $$\upmu $$ μ rad, corresponding to an absolute geometrical precision of $${\mathcal {O}}(1\,\upmu \text {m})$$ O ( 1 μ m ) on the monitor radial dimensions; and v) the very high bunch-crossing rate of 50 MHz during the Z-pole operation calls for fast readout electronics. Inspired by second-generation LEP luminosity monitors, which achieved an experimental precision of $$3.4 \times 10^{-4}$$ 3.4 × 10 - 4 on the absolute luminosity measurement (Abbiendi et al. in Eur Phys J C 14:373–425, 2000), a proposed ultra-compact solution is based on a sandwich of tungsten-silicon layers. A vigorous R&D programme is needed in order to ensure that such a solution satisfies the more challenging FCC-ee requirements.

The trigger and data acquisition system of the FASER experiment

The FASER experiment is a new small and inexpensive experiment that is placed 480 meters downstream of the ATLAS experiment at the CERN LHC. FASER is designed to capture decays of new long-lived particles, produced outside of the ATLAS detector acceptance. These rare particles can decay in the FASER detector together with about 500–1000 Hz of other particles originating from the ATLAS interaction point. A very high efficiency trigger and data acquisition system is required to ensure that the physics events of interest will be recorded. This paper describes the trigger and data acquisition system of the FASER experiment and presents performance results of the system acquired during initial commissioning.

Muon reconstruction and identification efficiency in ATLAS using the full Run 2 pp collision data set at $$\sqrt{s}=13$$ TeV

This article documents the muon reconstruction and identification efficiency obtained by the ATLAS experiment for 139 $$\hbox {fb}^{-1}$$ fb - 1 of pp collision data at $$\sqrt{s}=13$$ s = 13 TeV collected between 2015 and 2018 during Run 2 of the LHC. The increased instantaneous luminosity delivered by the LHC over this period required a reoptimisation of the criteria for the identification of prompt muons. Improved and newly developed algorithms were deployed to preserve high muon identification efficiency with a low misidentification rate and good momentum resolution. The availability of large samples of $$Z\rightarrow \mu \mu $$ Z → μ μ and $$J/\psi \rightarrow \mu \mu $$ J / ψ → μ μ decays, and the minimisation of systematic uncertainties, allows the efficiencies of criteria for muon identification, primary vertex association, and isolation to be measured with an accuracy at the per-mille level in the bulk of the phase space, and up to the percent level in complex kinematic configurations. Excellent performance is achieved over a range of transverse momenta from 3 GeV to several hundred GeV, and across the full muon detector acceptance of $$|\eta |<2.7$$ | η | < 2.7 .

Dark scalars and heavy neutral leptons at DarkQuest

The proposed DarkQuest beam dump experiment, a modest upgrade to the existing SeaQuest/SpinQuest experiment, has great potential for uncovering new physics within a dark sector. We explore both the near-term and long-term prospects for observing two distinct, highly-motivated hidden sector benchmark models: heavy neutral leptons and Higgs-mixed scalars. We comprehensively examine the particle production and detector acceptance at DarkQuest, including an updated treatment of meson production, and light scalar production through both bremsstrahlung and gluon-gluon fusion. In both benchmark models, DarkQuest will provide an opportunity to probe previously inaccessible interesting regions of parameter space on a fairly short timescale when compared to other proposed experiments.

A Vector Finder Toolkit for Track Reconstruction in MPD ITS

As a part of the future upgrade program of the Multi-Purpose Detector (MPD) experiment at the Nuclotron-Based Ion Collider Facility (NICA) complex, an Inner Tracking System (ITS) made of Monolitic Active Pixel Sensors (MAPSs) is proposed between the beam pipe and the Time Projection Chamber (TPC). It is expected that the new detector will enhance the experimental potential for the reconstruction of short-lived particles—in particular, those containing the open charm particle. To study the detector performance and select its best configuration, a track reconstruction approach based on a constrained combinatorial search was developed and implemented as a software toolkit called Vector Finder. This paper describes the proposed approach and demonstrates its characteristics for primary and secondary track finding in ITS, ITS-to-TPC track matching and hyperon reconstruction within the MPD software framework. The results were obtained on a set of simulated central gold–gold collision events at sNN=9 GeV with an average multiplicity of ∼1000 charged particles in the detector acceptance produced with the Ultra-Relativistic Quantum Molecular Dynamics (UrQMD) generator.

Production and electromagnetic decay of hyperons: a feasibility study with HADES as a phase-0 experiment at FAIR

A feasibility study has been performed in order to investigate the performance of the HADES detector to measure the electromagnetic decays of the hyperon resonances $$\Sigma (1385)^{0}$$ Σ ( 1385 ) 0 , $$\Lambda (1405)$$ Λ ( 1405 ) and $$\Lambda (1520)$$ Λ ( 1520 ) as well as the production of double strange baryon systems $$\Xi ^{-}$$ Ξ - and $$\Lambda $$ Λ $$\Lambda $$ Λ in p + p reactions at a beam kinetic energy of $$4.5\,{\mathrm{GeV}}$$ 4.5 GeV . The existing HADES detector will be upgraded by a new Forward Detector, which extends the detector acceptance into a range of polar angles that plays a crucial role for these investigations. The analysis of each channel is preceded by a consideration of the production cross-sections. Afterwards the expected signal count rates using a target consisting of either liquid hydrogen or polyethylene are summarized.

Study of excited $$\varvec{\varXi }$$ baryons with the $$\overline{\text{ P }}$$ANDA detector

The study of baryon excitation spectra provides insight into the inner structure of baryons. So far, most of the world-wide efforts have been directed towards $$N^*$$ N ∗ and $$\varDelta $$ Δ spectroscopy. Nevertheless, the study of the double and triple strange baryon spectrum provides independent information to the $$N^*$$ N ∗ and $$\varDelta $$ Δ spectra. The future antiproton experiment $$\overline{\text{ P }}$$ P ¯ ANDA will provide direct access to final states containing a $${\overline{\varXi }}\varXi $$ Ξ ¯ Ξ pair, for which production cross sections up to $$\mu \text{ b }$$ μ b are expected in $$\bar{\text{ p }}$$ p ¯ p reactions. With a luminosity of $$L=10^{31}$$ L = 10 31 cm$$^{-2}$$ - 2 s$$^{-1}$$ - 1 in the first phase of the experiment, the expected cross sections correspond to a production rate of $$\sim 10^6\, \text{ events }/\text{day }$$ ∼ 10 6 events / day . With a nearly $$4\pi $$ 4 π detector acceptance, $$\overline{\text{ P }}$$ P ¯ ANDA will thus be a hyperon factory. In this study, reactions of the type $$\bar{\text{ p }}$$ p ¯ p $$\rightarrow $$ → $${\overline{\varXi }}^{+}$$ Ξ ¯ + $$\varXi ^{*-}$$ Ξ ∗ - as well as $$\bar{\text{ p }}$$ p ¯ p $$\rightarrow $$ → $${\overline{\varXi }}^{*+}$$ Ξ ¯ ∗ + $$\varXi ^{-}$$ Ξ - with various decay modes are investigated. For the exclusive reconstruction of the signal events a full decay tree fit is used, resulting in reconstruction efficiencies between 3 and 5%. This allows high statistics data to be collected within a few weeks of data taking.

Towards a computer vision particle flow

In High Energy Physics experiments Particle Flow (PFlow) algorithms are designed to provide an optimal reconstruction of the nature and kinematic properties of the particles produced within the detector acceptance during collisions. At the heart of PFlow algorithms is the ability to distinguish the calorimeter energy deposits of neutral particles from those of charged particles, using the complementary measurements of charged particle tracking devices, to provide a superior measurement of the particle content and kinematics. In this paper, a computer vision approach to this fundamental aspect of PFlow algorithms, based on calorimeter images, is proposed. A comparative study of the state of the art deep learning techniques is performed. A significantly improved reconstruction of the neutral particle calorimeter energy deposits is obtained in a context of large overlaps with the deposits from charged particles. Calorimeter images with augmented finer granularity are also obtained using super-resolution techniques.

Measurement of $$W^{\pm }$$-boson and Z-boson production cross-sections in pp collisions at $$\sqrt{s}=2.76$$ TeV with the ATLAS detector

The production cross-sections for $$W^{\pm }$$W± and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb$$^{-1}$$-1 collected at a centre-of-mass energy $$\sqrt{s}=2.76$$s=2.76 TeV. The decay channels $$W \rightarrow \ell \nu $$W→ℓν and $$Z \rightarrow \ell \ell $$Z→ℓℓ are used, where $$\ell $$ℓ can be an electron or a muon. The cross-sections are presented for a fiducial region defined by the detector acceptance and are also extrapolated to the full phase space for the total inclusive production cross-section. The combined (average) total inclusive cross-sections for the electron and muon channels are: $$\begin{aligned} \sigma ^{\text {tot}}_{W^{+}\rightarrow \ell \nu }= & {} 2312 \pm 26\ (\text {stat.})\\&\pm 27\ (\text {syst.}) \pm 72\ (\text {lumi.}) \pm 30\ (\text {extr.})~\text {pb} , \\ \sigma ^{\text {tot}}_{W^{-}\rightarrow \ell \nu }= & {} 1399 \pm 21\ (\text {stat.})\ \pm 17\ (\text {syst.}) \\&\pm 43\ (\text {lumi.}) \pm 21\ (\text {extr.})~\text {pb} , \\ \sigma ^{\text {tot}}_{Z \rightarrow \ell \ell }= & {} 323.4 \pm 9.8\ (\text {stat.}) \pm 5.0\ (\text {syst.})\\&\pm 10.0\ (\text {lumi.}) \pm 5.5 (\text {extr.}) ~\text {pb} . \end{aligned}$$σW+→ℓνtot=2312±26(stat.)±27(syst.)±72(lumi.)±30(extr.)pb,σW-→ℓνtot=1399±21(stat.)±17(syst.)±43(lumi.)±21(extr.)pb,σZ→ℓℓtot=323.4±9.8(stat.)±5.0(syst.)±10.0(lumi.)±5.5(extr.)pb.Measured ratios and asymmetries constructed using these cross-sections are also presented. These observables benefit from full or partial cancellation of many systematic uncertainties that are correlated between the different measurements.

The KLOE-2 experiment at DAΦNE

The KLOE-2 Collaboration succesfully ended its data-taking collecting a total integrated luminosity of 5.5 fb−1 at the peak of the φ(1020) resonance at the DAΦNE collider of the Frascati LNF. New detectors have been added to the KLOE apparatus to improve the detector acceptance, the tracking capability, and also to be able to tag the scattered electrons in γγ processes. By summing the new data sample to the old one of the previous KLOE data-taking ended in 2006, a total of about 8 fb−1 has been collected, corresponding to 24 billions of φ produced. The measurement program of KLOE-2 includes precision studies on kaon and other light mesons, hadronic cross-section, and dark force searches.