Measuring the rate at which the long-lived, neutral kaon decays into a neutral pion, neutrino, and anti-neutrino allows physicists an opportunity to test precise predictions made by the Standard Model. Differences between theoretical predictions and experimental measurements may point to new physics. Not only does the Standard Model predict a very low probability at approximately 3 $K_L \to π^0 ν\barν$ decays in 100 billion $K_L$ decays, but many of the common decays leave false signals in the detector that look the same as the true signal. Charged decays have been studied to determine the required detection efficiency necessary to eliminate them. The conclusion of these studies is that a reduction by a factor of $1/(3\times10^9)$ will be required to achieve the 10:1 signal to charged background ratio necessary for the experiment.
We are investigating the feasibility of performing a measurement of $BR(K_L\rightarrowπ^0ν\barν)$ using a high-energy secondary neutral beam at the CERN SPS in a successor experiment to NA62. The timescale would require many years; we assume that the experiment would be ready at the start of LHC Run 4. Some preliminary conclusions from our feasibility studies, design challenges faced and sensitivity obtainable for the measurement are here presented.
The availability of high intensity kaon beams at the CERN SPS North Area gives rise to unique possibilities for sensitive tests of the Standard Model in the quark flavor sector. Precise measurements of the branching ratios for the flavor-changing neutral current decays $K\toπν\barν$ can provide unique constraints on CKM unitarity and, potentially, evidence for new physics. Building on the success of the NA62 experiment, plans are taking shape at CERN for a comprehensive program that will include experimental phases to measure the branching ratio for $K^+\toπ^+ν\barν$ to ~5% and to $K_L\toπ^0ν\…
Searches for heavy neutrinos can be successfully performed by fixed target experiments at the CERN SPS. New results obtained by the NA62 and NA48/2 kaon experiments are summarized in this paper. The physics potential of future projects exploiting SPS protons with beam dump facilities to enlarge the sensitivity to heavy neutrinos above the kaon mass limit are also outlined.
We report results on $ψ'$ production as a function of centrality as measured by experiment NA50, at the CERN/SPS, in Pb-Pb collisions at an incident energy of 158 GeV per nucleon.
NA64 is a fixed target experiment at the CERN SPS designed as a hermetic general purpose detector to search for Dark Sector physics in missing energy events from electron/positron, hadrons, and muon scattering off nuclei. In this contribution to the FIPs 2022 workshop, we review the current status and prospects of NA64.
Experiment NA49 at the Cern SPS uses a large acceptance detector for a systematic study of particle yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results for Pb+Pb collisions at 40, 80 and 158 A*GeV beam energy are shown and compared to measurements at lower and higher energies.
New data from the NA49 experiment at the CERN SPS concerning hadron+proton and hadron+nucleus interactions are discussed and compared to nucleus+nucleus collisions. Detailed information on baryonic momentum distributions and nuclear enhancement factors for kaons and cascade baryons are extracted.
The Search for Hidden Particles (SHiP) Collaboration has shown that the CERN SPS accelerator with its 400 $\mathrm{\small GeV/c}$ proton beam offers a unique opportunity to explore the Hidden Sector. The proposed experiment is an intensity frontier experiment which is capable of searching for hidden particles through both visible decays and through scattering signatures from recoil of electrons or nuclei. The high-intensity experimental facility developed by the SHiP collaboration is based on a number of key features and developments which provide the possibility of probing a large part of the…
An experimental proposal to measure Br($K^+ \to π^+ ν\barν$) has been submitted at the CERN SPSC. The goal is to collect ~80 $K^+\to π^+ ν\barν$ events with signal to background ratio of 10:1 in two years of data taking. This will allow determination of the CKM parameter $V_{td}$ with ~10% accuracy.
The phenomenology in the neutrino sector requires physics beyond the Standard Model. One possibility is the existence of new massive leptonic states which could be probed at the high intensity machines. The present results on heavy neutral leptons from the study of kaon decays in flight with the NA48/2 and NA62 experiments are presented and the future prospects for such searches at CERN SPS are discussed.
This article gives a brief overview of some recent advances in our understanding of the physics of dense strongly interacting matter, from measurements done at the CERN SPS. The presently available results are very interesting, and are likely to reflect the production of a new state of matter in central Pb-Pb collisions, at the highest SPS energies. However, important questions require further work. Particular emphasis is given to developments made since the Quark Matter 1999 conference, and to issues that justify the continuation of the SPS heavy ion physics program beyond year 2000.
The aim of the NA48 experiment at the CERN SPS is to measure direct CP violation in neutral kaon decays thus determining the parameter $ε'/ε$ with an accuracy of $2\times 10^{-4}$. The advantages of NA48 with respect to previous experiments are high statistics and reduced systematic effects. The principle of the experiment and the performance of the detector components are presented.
Precise measurements of the branching ratios for the flavor-changing neutral current decays $K\toπν\barν$ can provide unique constraints on CKM unitarity and, potentially, evidence for new physics. It is important to measure both decay modes, $K^+\toπ^+ν\barν$ and $K_L\toπ^0ν\barν$, since different new physics models affect the rates for each channel differently. The NA62 experiment at the CERN SPS will measure the BR for the charged channel to better than 20%. The BR for the neutral channel has never been measured. We are designing the KLEVER experiment to measure BR($K_L\toπ^0ν\barν$) to $\s…
In this article the NA61/SHINE detector will be presented which is a large acceptance hadron spectrometer at the CERN SPS. It allows for a precise study of particle production from interactions of a 30 GeV proton beam in a carbon target in order to predict the neutrino flux of the T2K experiment at J-PARC, Japan. Requirements for the T2K experiment will be discussed together with the ongoing NA61 measurements. In particular preliminary NA61 results on pion production and cross section measurements from the 2007 pilot run will be shown.
The NA48/2 experiment at the CERN SPS carried out data taking in 2003 and 2004. Analysis of the selected data samples of 7,146 $K^\pm\toπ^\pm e^+e^-$ decay candidates with 0.6% background, 1,164 $K^\pm\toπ^\pmγγ$ candidates with 3.3% background, and 120 $K^\pm\toπ^\pmγe^+e^-$ candidates with 6.1% background allowed precise measurements of branching fractions and other characteristics of these rare kaon decays.
Recent results a future prospects of the NA62 experiment at CERN SPS are presented. The NA62 experiment performed the most precise measurement of the ratio $R_K$ of the $K^+\rightarrow e^\pmν$ and K^+\rightarrow μ^\pmν$ decay rates using the full data set collected in 2007. The result is in agreement with the Standard Model expectation. The ultra-rare decay $K^+\rightarrowπ^+ν\barν$ is an excellent processes to make tests of new physics at the highest scale complementary to the LHC thanks to their theoretically cleanness. The NA62 experiment at CERN SPS aims to collect of the order of 100 $K^+…
In the spirit of establishing a fair reference for nucleus-nucleus collisions, results on stopping and baryon transfer, correlations of the p+p interaction and their consequences are shown. In the discussion of new results from nucleus-nucleus collisions the emphasis is on strange meson and baryon production at different energies - for the first time at 40 GeV A - with the study of light nuclei.
The NA38 and NA50 experiments at the CERN SPS have measured charmonium production in different colliding systems with the aim of observing a phase transition from ordinary hadronic matter towards a state in which quarks and gluons are deconfined (Quark Gluon Plasma, QGP). In fact it was predicted that the J/psi yield should be suppressed in deconfined matter. The analysis of the data collected by the NA50 experiment with Pb-Pb collisions at 158 GeV/c per nucleon shows that the J/psi is anomalously suppressed in central collisions and the observed pattern can be considered as a strong indicatio…
The Chinese large-area violet-light-sensitive silicon photodiode PIN is one of the candidates of the lead tungstate crystal detector readout component of the photon spectrometer in the large heavy ion collision experiment. The PIN diode was assembled with the lead tungstate crystal and the low-noise preamplifier into a complete detector unit. The beam test was carried out on the SPS accelerator at CERN. The energy resolution was measured with the electron beam energy ranging from 5 to 40 GeV. The summation correction method was discussed, and an excellent linearity of the nominal beam energy v…
Precise measurements of the branching ratios for the flavor-changing neutral current decays $K\toπν\barν$ can provide unique constraints on CKM unitarity and, potentially, evidence for new physics. It is important to measure both decay modes, $K^+\toπ^+ν\barν$ and $K_L\toπ^0ν\barν$, since different new physics models affect the rates for each channel differently. The goal of the NA62 experiment at the CERN SPS is to measure the BR for the charged channel to within 10%. For the neutral channel, the BR has never been measured. KOTO, an experiment at J-PARC, should have enough data for the first …
Simulation of the CERN crystal-extraction experiments at the SPS, including the real crystal geometry and SPS parameters, as well as multiple turns and passes, has been performed. Two crystals with different geometry have been tried. We argue that in both cases the extraction experiment suffered from the crystal edge imperfection. For the experimental conditions reproduced, the efficiency of the first (twisted) crystal was found to be 12-18% (peak) in the angular range of 140-260 microrad (FWHM), depending on the vertical beam position at the crystal location. For the second (U-shaped) crystal…
The branching ratio (BR) for the decay K^+ \to π^+ν\barν is a sensitive probe for new physics. The NA62 experiment at the CERN SPS will measure this BR to within about 10%. To reject the background from dominant kaon decays with final state photons, the large-angle photon vetoes (LAVs) must detect photons of energy as low as 200 MeV with an inefficiency of less than 10^{-4}. The LAV detectors make use of lead glass blocks recycled from the OPAL electromagnetic calorimeter barrel. We describe the mechanical design and challenges faced during construction, the characterization of the lead glass …
Precise measurements of the branching ratios for the $K\toπν\barν$ decays can provide unique constraints on CKM unitarity and, potentially, evidence for new physics. It is important to measure both decay modes, $K^+\toπ^+ν\barν$ and $K_L\toπ^0ν\barν$, since different new physics models affect the rates for each channel differently. We are investigating the feasibility of performing a measurement of BR($K_L\toπ^0ν\barν$) using a high-energy secondary neutral beam at the CERN SPS in a successor experiment to NA62. The planned experiment would reuse some of the NA62 infrastructure, including poss…
The centrality dependence of rapidity distributions of pions in Pb+Pb reactions can be understood by imposing local energy-momentum conservation in the longitudinal "fire-streaks" of excited matter. With no tuning nor adjustment to the experimental data, the rapidity distribution of pions produced by the fire-streak which we obtained from Pb+Pb collisions reproduces the shape of the experimental pion rapidity distribution in p+p interactions, measured by the NA49 Collaboration at the same energy. The observed difference in the absolute normalization of this distribution can be explained by the…
The NA62 experiment at SPS is a continuation of the long standing CERN kaon physics program. The high statistics and the unprecedent precision allow to probe the Standard Model and test the description of the strong interactions at low energy. The final results on the the lepton universality test by measuring the ratio $R_K = Γ(K^{+}\to e^{+}ν) / Γ(K^{+}\to μ^{+}ν)$ and the study of the $K^\pm\toπ^{\pm}γγ$ decay are presented. The major goal of the NA62 experiment is to perform a measurement of the $Br(K^{+} \to π^{+} ν\barν)$ with a precision of 10% in two years of data taking. The detector s…
The NA48/2 has collected the largest amount of $K\to3 π$. The charge asymmetry parameter $A_g$, sensitive to CP violation effects, has been measured with a precision of $10^{-4}$ (preliminary) both in the three charged pion mode ("charged" mode) and in the mode with two neutral pions in the final state ("neutral" mode). The Dalitz plot structure in the "neutral" mode will be discussed to point out the effects of the charged pion rescattering. The new preliminary measurement of the Dalitz plot parameters in the charged mode will be presented
Multiplicity fluctuations were investigated in Ar+Sc collisions at 13A, 19A, 30A, 40A, 75A, 150A GeV/c using the NA61/SHINE detector at the SPS. Centrality selection is based on the nucleon-spectator energy in the forward hemisphere as measured by the Projectile spectator detector. Preliminary results on the scaled variance ω and the strongly intensive measure Ω were obtained for the multiplicity distribution of all, negatively and positively charged hadrons. Results are discussed and compared with p+p results and Pb+Pb data of NA49 and EPOS 1.99 simulations.
We present the final results of experiment NA50 on charmonia production in Pb-Pb interactions at 158 A GeV. A strong increasing suppression is observed with increasing centrality, for both the jpsi and psiprime resonances. We also present new developments regarding the jpsi and psiprime normal nuclear absorption determinations deduced from proton-nucleus data only. Their comparison with Pb-Pb results allows us to conclude that the jpsi anomalous suppression sets in at mid-centralities while the S-U results show a reasonable agreement with the p-A behavior. The psiprime suffers a significantly …
We examine Pb+Pb collisions at CERN SPS energy 158 A GeV, by employing the earlier developed and recently refined parton-cascade/cluster-hadronization model and its Monte Carlo implementation. This space-time model involves the dynamical interplay of perturbative QCD parton production and evolution, with non-perturbative parton-cluster formation and hadron production through cluster decays. Using computer simulations, we are able to follow the entwined time-evolution of parton and hadron degrees of freedom in both position and momentum space, from the instant of nuclear overlap to the final yi…
Experiments at the CERN SPS: first signals of deconfinement
INFN Padova（意大利国家核物理研究所帕多瓦分部）；CERN（欧洲核子研究组织）；Jan Kochanowski University（扬·科哈诺夫斯基大学）；Universidad Nacional Autonoma de Mexico（墨西哥国立自治大学）；Czech Technical University (ČVUT)（捷克理工大学）；INFN Torino（意大利国家核物理研究所都灵分部）；Weizmann Institute of Science（魏茨曼科学研究所）；University of Cagliari（卡利亚里大学）；INFN Cagliari（意大利国家核物理研究所卡利亚里分部）
In the DsTau experiment at the CERN SPS, an independent and direct way to measure tau neutrino production following high energy proton interactions was proposed. As the main source of tau neutrinos is a decay of Ds mesons, produced in proton-nucleus interactions, the project aims at measuring a differential cross section of this reaction. The experimental method is based on a use of high resolution emulsion detectors for effective registration of events with short lived particle decays. Here we present the motivation of the study, details of the experimental technique, and the first results of…
The J/psi suppression observed by the NA50 experiment is one of the most striking signatures for quark gluon plasma formation in Pb-Pb collisions at 158 AGeV. The J/psi production has been studied as a function of the centrality of the collision estimated via the forward energy EZDC released in a zero degree calorimeter (ZDC). The study of the correlation between the number of participant nucleons in the collisions, Npart, and EZDC allows to check whether the J/psi suppression pattern vs. EZDC is compatible with a sudden J/psi suppression mechanism expressed as a function of Npart.
An important approach to studying high-energy cosmic rays is the investigation of the properties of extensive air showers; however, the lateral distribution of particles in simulations of such showers strongly depends on the applied model of low-energy hadronic interactions. It has been shown that many constraints to be applied to these models can be obtained by studying identified-particle spectra from accelerator collisions, in the energy range of the CERN Super Proton Synchrotron. Here we present measurements of the pion production cross-section obtained by the NA61/SHINE experiment at the …
In this paper, we discuss an experimental layout for the two-crystals scenario at the Super Proton Synchrotron (SPS) accelerator. The research focuses on a fixed target setup at the circulating machine in a frame of the Physics Beyond Colliders (PBC) project at CERN. The UA9 experiment at the SPS serves as a testbench for the proof of concept, which is planning to be projected onto the Large Hadron Collider (LHC) scale. The presented in the text configuration was used for the quantitative characterization of the deflected particle beam by a pair of bent silicon crystals. For the first time in …
The region of high baryonic densities of the QCD phase diagram is the object of several studies focused on the investigation of the order of the phase transition and the search for the critical point. The rare probes, which include electromagnetic observables and heavy quark production, are experimentally challenging to access as they require large integrated luminosities that could be studied with fixed-target experiments. A future experiment, NA60+ at CERN, is being proposed to access this region and perform accurate measurements of the dimuon spectrum up to the charmonium region and study c…
Inclusive pion production at high transverse momenta (p_T > 2 GeV/c) in nucleus-nucleus (A+A) collisions at CERN SPS (sqrt(s_NN)~20 GeV) is revisited and systematically compared to all existing proton-proton data in the same range of center-of-mass energies. The ratio of A+A to p+p pion cross-sections (nuclear modification factor) for 0-8% central Pb+Pb, Pb+Au and S+Au reactions does not show a strong enhancement as a function of p_T as previously found, but is consistent with scaling with the number of nucleon-nucleon (NN) collisions. Neutral pion yields per NN collision in head-on Pb+Pb reac…
We evaluate the spectra of produced particles (pions, kaons, antiprotons) from partonic cascades which may develop in the wake of heavy-ion collisions at CERN SPS energies and which may hadronize by formation of clusters which decay into hadrons. Using the experimental data obtained by NA35 and NA44 collaborations for S+S and Pb+Pb collisions, we conclude that the Monte Carlo implementation of the recently developed parton-cascade/cluster-hadronization model provides a reasonable description of the distributions of the particles produced in such collisions. While the rapidity distribution of t…
The Kaon physics program at CERN will be shortly presented, addressing the most recent results from the NA48/2 and NA62 experiments at the CERN SPS and future prospects.
Results are presented for directed flow of negatively charged pions measured relative to the spectator plane in Pb+Pb collisions at the beam energy 40A GeV recorded by the NA49 experiment at CERN. The measure-ments were performed as a function of rapidity and transverse momentum in two classes of collision centrality. The projectile spectator symmetry plane is estimated using the transverse segmentation of the forward hadron calorimeters. Analysis details related to event selection and particle dentification are provided along with a description of the procedure used to apply corrections for t…
The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. These goals are to be achieved by performing a two dimensional phase diagram (T-μ_B) scan by measurements of hadron production properties in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of collision energy and system size. Close to the critical point an increase of fluctuations is predicted. In this contribution preliminary results on transverse momentum fluctuations and two-particle pseudorapidity/azimuthal angle c…
The problem of pinning down the critical point of strongly interacting matter still puzzles the community. One of the answers suspected to emerge in the near future will surely come from NA61/SHINE - a fixed-target experiment aiming to discover the critical point as well as to study the properties of the onset of deconfinement. This goal will be pursued by obtaining precise data on hadron production in proton-proton, proton-nucleus and nucleus-nucleus interactions in a wide range of system size and collision energy. This contribution presents new results on inclusive spectra of identified hadr…
Results of resonance searches in the Xi- pi-, Xi- pi+, antiXi+ pi- and antiXi+ pi+ invariant mass spectra in proton-proton collisions at sqrt{s}=17.2 GeV are presented. Evidence is shown for the existence of a narrow Xi- pi- baryon resonance with mass of 1.862+/-0.002 GeV/c^2 and width below the detector resolution of about 0.018 GeV/c^2. The significance is estimated to be 4.0 sigma. This state is a candidate for the hypothetical exotic Xi_(3/2)^-- baryon with S = -2, I = 3/2 and a quark content of (d s d s ubar). At the same mass a peak is observed in the Xi- pi+ spectrum which is a candidat…
With the Large Hadron Collider entering its third year of granting us insight into the highest collision energies to date, one should nevertheless keep in mind the unexplored physics potential of lower energies. A prime example here is the NA61/SHINE experiment at the CERN Super Proton Synchrotron. Using its large-acceptance hadronic spectrometer, SHINE aims to accomplish a number of physics goals: measuring spectra of identified hadrons in hadron-nucleus collisions to provide reference for accelerator neutrino experiments and cosmic-ray observatories, investigating particle properties in the …
NA61/SHINE is a fixed target experiment designed to study hadron-proton, hadron-nucleus and nucleus-nucleus interactions at the CERN Super-Proton-Synchrotron. In this proceeding we present results on spectra of identified hadrons produced in pion-carbon production interactions, which are of fundamental importance to improve the extensive air shower modeling, and hence the interpretation of ultra-high-energy-cosmic-rays measurements. In particular, our measurements of (anti)baryons and $ρ^0$ production in pion-carbon interactions can contribute to improve the predictions of muon production by a…
A light $Z'$ vector boson coupled to the second and third lepton generations through $L_μ-L_τ$ current with mass below 200 MeV provides a very viable explanation in terms of new physics to the recently confirmed $(g-2)_μ$ anomaly. This boson can be produced in the bremsstrahlung reaction $μN \rightarrow μN Z'$ after a high energy muon beam collides with a target. NA64$μ$ is a fixed-target experiment using a 160 GeV muon beam from the CERN Super Proton Synchrotron accelerator looking for the $Z'$ production and its subsequent decays, $Z'\rightarrow invisible$. In this paper, we present the stud…
We report on a direct search for sub-GeV dark photons (A') which might be produced in the reaction e^- Z \to e^- Z A' via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The A's would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75\cdot 10^{9} electrons on target. We set new limits on the γ-A' mixing strength and exclude the invisible A' with a mass < 100 MeV as an explanation of the muon g_μ-2 anomaly.
Pion production in nuclear collisions at the SPS is investigated with the aim to search, in a restricted domain of the phase diagram, for power-laws in the behavior of correlations which are compatible with critical QCD. We have analyzed interactions of nuclei of different size (p+p, C+C, Si+Si, Pb+Pb) at 158$A$ GeV adopting, as appropriate observables, scaled factorial moments in a search for intermittent fluctuations in transverse dimensions. The analysis is performed for $π^+π^-$ pairs with invariant mass very close to the two-pion threshold. In this sector one may capture critical fluctuat…
We analyze the newest data from the NA61/SHINE collaboration which, in addition to previous results on pions and kaons, include mean multiplicities of $p$, $Λ$, and $ϕ$-mesons produced in inelastic proton-proton (p+p) interactions at $\sqrt{s_{NN}}=6.3-17.3$~GeV. The canonical ensemble formulation of the ideal hadron resonance gas (HRG) model is used with exact conservation of net baryon number $B=2$, electric charge $Q=2$, and strangeness $S=0$. The chemical freeze-out parameters in p+p interactions are obtained and compared to those in central nucleus-nucleus collisions. Several features of …
