Vito Palladino

The proton-antiproton total cross section was measured at the CM energy √s = 546 GeV. The result is σtot = 61.9± 1.5 mb. The ratio of the elastic to the total cross section is σeℓ/σtot = 0.215±0.005. A comparison to the lower energy data shows that the increase of the total cross section with energy is very close to a log2s behaviour.

Proton-antiproton elastic scattering was measured at the CERN SPS Collider at the centr-of-mass energy s=546 GeV in the Coulomb interference region. The data provide information on the phase of the hadronic amplitude in the forward direction. The conventional analysis gives for the ratio ϱ of the real to the imaginary part of the hadronic amplitude the result ϱ=0.24±0.04.

Proton-antiproton elastic scattering was measured at the CM energy √s = 546 GeV in the four-momentum transfer range 0.03<−t<0.32GeV2 For −<0.15GeV2 the data are well described by a simple exponential form exp(bt) with slope parameter b=15.2±0.2GeV−2. This value is significantly larger than the one measured in the region 0.21<−t<0.50 GeV2.

A precision measurement of the ratio RK of the rates of kaon leptonic decays K±→e±ν and K±→μ±ν with the full data sample collected by the NA62 experiment at CERN in 2007–2008 is reported. The result, obtained by analysing ∼150000 reconstructed K±→e±ν candidates with 11% background contamination, is RK=(2.488±0.010)×10−5, in agreement with the Standard Model expectation.

Proton-antiproton elastic scattering was measured at the center-of-mass energy s=546 GeV in the four-momentum transfer range 0.45⩽−⩽1.55GeV2. The shape of the t-distribution is quite different from that observed in proton-proton scattering at the ISR. Rather than a dip-bump structure, a kink is present at − ≈0.9GeV2 followed by a shoulder. The cross section at the second maximum is more than one order of magnitude higher than at the ISR.

Single diffraction dissociation was measured in the reaction p¯p→p¯X at the centre-of-mass energy √s = 546 GeV. The mass M of the system X was deduced from the pseudorapidity distribution of the observed charged tracks. The cross section of single diffraction dissociation for M2/s⩽0.05isσsd=9.4 ± 0.7 mb. Comparison to the ISR data shows that σsd increases with energy less fast than the total and the elastic cross sections.

First results on the measurement of the elastic and total cross section at the CERN pp̄ Collider are presented. Combining the measurement of elastic scattering at low momentum transfer with the rate of inelastic interactions, a value of the total cross section of 66 mb with a 10% statistical error was obtained.

Proton-antiproton elastic scattering was measured at the centre-of-mass energy s = 630 GeV in the four-momentum transfer range 0.7 ⩽ − t ⩽ 2.2 GeV2. The new data confirm our previous results at s = 546 GeV on the presence of a break in the t-distribution at −t ≃ 0.9 GeV2 which is followed by a shoulder, and extend the momentum transfer range to larger values. The t-dependence of the differential cross section beyond the break is discussed.

The reaction pp → pX was studied at a centre-of-mass energy s = 540 GeV by measuring the momentum spectrum of the antiproton. Data are presented in the four-momentum transfer range 05 < −t < 1.2GeV2. The shape of the mass distribution of the system X shows a diffractive component as already observed at lower energies. The differential cross section scales approximately with energy when compared to the ISR data.

A study of the dynamics of the rare decay K±→π±γγ has been performed on a sample of 232 decay candidates, with an estimated background of 17.4±1.1 events, collected by the NA62 experiment at CERN in 2007. The results are combined with those from a measurement conducted by the NA48/2 Collaboration at CERN. The combined model-independent branching ratio in the kinematic range z=(mγγ/mK)2>0.2 is BMI(z>0.2)=(0.965±0.063)×10−6, and the combined branching ratio in the full kinematic range assuming a Chiral Perturbation Theory description is B(Kπγγ)=(1.003±0.056)×10−6. A detailed comparison of the results with the previous measurements is performed.

The reaction pp → pX was studied as a function of the mass M of the system X at the centre-of-mass energy s = 546 GeV in the kinematical region where diffraction dissociation dominates. The pseudorapidity distribution of charged tracks, produced in the fragmentation of the system X, is well described within the limits of cylindrical phase space. The fragments of the X-system behave very similarly to the products of non-diffractive inelastic collisions at s = M.

Proton-antiproton elastic scattering was measured at a centre of mass energy s = 540 GeV. In the four-momentum transfer range 0.21 < −t < 0.50 GeV2 the t-distribution of about 7000 events is well represented by the exponential shape exp (bt) with slope parameter b = 13.7 ± 0.3 GeV−2. A new measurement of the slope for −t < 0.19 GeV2 confirms our earlier result, giving evidence for a change of slope of about 4 GeV−2 around −l̷ ≈ 0.15 GeV2.

A precision test of lepton flavour universality has been performed by measuring the ratio RK of kaon leptonic decay rates K+ --> e+nu and K+ --> mu+nu in a sample of 59813 reconstructed K+ --> e+nu candidates with (8.71 +- 0.24)% background contamination. The result RK = (2.487 +- 0.013) * 10^{-5} is in agreement with the Standard Model expectation.

The NA62 experiment collected a large sample of charged kaon decays in 2007 with a highly efficient trigger for decays into electrons. A measurement of the $\pi^0$ electromagnetic transition form factor slope parameter from $1.11\times10^{6}$ fully reconstructed $K^\pm \to \pi^\pm \pi^0_D, \pi^0_D \to e^+ e^-\gamma$ events is reported. The measured value $a = (3.68 \pm 0.57)\times10^{-2}$ is in good agreement with theoretical expectations and previous measurements, and represents the most precise experimental determination of the slope in the time-like momentum transfer region.

The NA62 experiment recorded a large sample of $K^+ \rightarrow \mu^+ \nu_{\mu}$ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range $2 \times 10^{-6}$ to $10^{-5}$ have been set on the squared mixing matrix element $|U_{\mu4} |^2$ between muon and heavy neutrino states, for heavy neutrino masses in the range 300-375 MeV/$c^2$. The result extends the range of masses for which upper limits have been set on the value of $|U_{\mu4} |^2$ in previous production search experiments.

Proton-antiproton elastic scattering at a centre-of-mass energy of 540 GeV was measured in the four-momentum transfer range 0.05 < −t < s.19 GeV2. The t-distribution can be fitted by the exponential exp(b) with b=17.2±1.0 GeV−2. This result indicates a rapid decrease of the width of the diffraction peak between ISR and Collider energies.

We have measured the cross section for inverse muon decay in the CERN neutrino wide band beam. From 4808 events observed in the CHARM II detector we derived for the Born term of the asymptotic cross section slope the result (18.16±1.36) × 10−42 cm2 GeV−1. This cross section is in good agreement with the standard model prediction and allows to constrain the scalar coupling of the electron and muon to their neutrinos to |gLLS|2<0.405 at 90% CL.

We describe the apparatus used in experiment UA4 to study proton-antiproton elastic and inelastic interactions at the CERN SPS Collider. Elastically scattered particles, travelling at very small angles, are observed by detectors placed inside movable sections (“Roman pots”) of the SPS vacuum chamber. The deflection in the field of the machine quadrupoles allow the measurement of the particle momentum. Inelastic interactions are observed by a left-right symmetric system of trigger counter hodoscopes and drift-chamber telescopes. The apparatus reconstructs the interaction vertex and measures the pseudorapidity η of charged particles in the range 2.5 < ‖η‖ < 5.6.

The results of the measurements of the double-differential production cross-sections of pions in p-C and $\pi^\pm$-C interactions using the forward spectrometer of the HARP experiment are presented. The incident particles are 12 GeV/c protons and charged pions directed onto a carbon target with a thickness of 5% of a nuclear interaction length. For p-C interactions the analysis is performed using 100035 reconstructed secondary tracks, while the corresponding numbers of tracks for $\pi^-$-C and $\pi^+$-C analyses are 106534 and 10122 respectively. Cross-section results are presented in the kinematic range 0.5 GeV/c $\leq p_{\pi} <$ 8 GeV/c and 30 mrad $\leq \theta_{\pi} <$ 240 mrad in the laboratory frame. The measured cross-sections have a direct impact on the precise calculation of atmospheric neutrino fluxes and on the improved reliability of extensive air shower simulations by reducing the uncertainties of hadronic interaction models in the low energy range.

This paper reports on the charged pion production yields measured by the SPY/NA56 experiment for 450 GeV/c proton interactions on beryllium targets. The present data cover a secondary momentum range from 7 GeV/c to 135 GeV/c in the forward direction. An experimental accuracy ranging from 5 to 10%, depending on the beam momentum, has been achieved, limited mainly by the knowledge of the beam acceptance. These results will be relevant in the calculation of neutrino fluxes in present and future neutrino beams.

A study of quasielastic $\ensuremath{\omega}$ photoproduction where the $\ensuremath{\omega}$ was detected in its ${\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ decay mode is reported. The recoil proton's angle was detected with a nonmagnetic spectrometer allowing a full reconstruction of the final state. Differential cross sections for $0.1&lt;|t|&lt;1.2$ ${\mathrm{GeV}}^{2}$ are presented, providing a test of the vector-meson dominance model over an extensive energy and momentum transfer range. The shape of the differential cross section agrees with that seen in both elastic $\ensuremath{\gamma}p$ and $\ensuremath{\pi}p$ scattering as expected from this model.

The particle identification (PID) methods used for the calculation of secondary pion yields with the HARP forward spectrometer are presented. Information from time of flight and Cherenkov detectors is combined using likelihood techniques. The efficiencies and purities associated with the different PID selection criteria are obtained from the data. For the proton–aluminium interactions at 12.9 GeV/c incident momentum, the PID efficiencies for positive pions are 86% in the momentum range below 2 GeV/c, 92% between 2 and 3 GeV/c and 98% in the momentum range above 3 GeV/c. The purity of the selection is better than 92% for all momenta. Special emphasis has been put on understanding the main error sources. The final PID uncertainty on the pion yield is 3.3%.

Measurements of double-differential charged pion production cross-sections in interactions of 12 GeV/c protons on O_2 and N_2 thin targets are presented in the kinematic range 0.5 GeV/c < p_{\pi} < 8 GeV/c and 50 mrad < \theta_{\pi} < 250 mrad (in the laboratory frame) and are compared with p--C results. For p--N_2 (p--O_2) interactions the analysis is performed using 38576 (7522) reconstructed secondary pions. The analysis uses the beam instrumentation and the forward spectrometer of the HARP experiment at CERN PS. The measured cross-sections have a direct impact on the precise calculation of atmospheric neutrino fluxes and on the improved reliability of extensive air shower simulations by reducing the uncertainties of hadronic interaction models in the low energy range. In particular, the present results allow the common hypothesis that p--C data can be used to predict the p--N_2 and p--O_2 pion production cross-sections to be tested.

In the tagged-photon beam at Fermilab, differential cross sections were measured for the elastic scattering of photons on a liquid-hydrogen target. The diffractive forward peak was measured for photon energies between 50 and 130 GeV and $|t|$ values between 0.07 and 1.20 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. The shape of the diffraction peak is similar to that seen in $\ensuremath{\pi}\ensuremath{-}p$ scattering. The magnitude is that predicted by the optical theorem.

The branching ratio for the decay $K^+ \to \pi^+\nu\bar{\nu}$ is sensitive to new physics; the NA62 experiment will measure it to within about 10%. To reject the dominant background from channels with final state photons, the large-angle vetoes (LAVs) must detect particles with better than 1 ns time resolution and 10% energy resolution over a very large energy range. Our custom readout board uses a time-over-threshold discriminator coupled to a TDC as a straightforward solution to satisfy these requirements. A prototype of the readout system was extensively tested together with the ANTI-A2 large angle veto module at CERN in summer 2010.

The NA62 experiment [1] will measure the BR(K+→π+ν) to within about 10%. To reject the dominant background from final state photons, the large-angle vetoes (LAVs) must detect particles with better than 1 ns time resolution and 10% energy resolution over a very large energy range. A low threshold, large dynamic range, Time-over-threshold based solution has been developed for the LAV front end electronics. Our custom 32 channel 9U board uses a pair of low threshold discriminators for each channel to produce LVDS logic signals. The achieved time resolution obtained in laboratory, coupled to an HPTDC based readout board, is ∼ 150 ps.

A 2150×2150 mm2 registration area drift chamber capable of working in vacuum is presented. Thin-wall tubes (straws) of a new type are used in the chamber. A large share of these 9.80 mm diameter drift tubes are made in Dubna from metalized 36 µm Mylar film welded along the generatrix using an ultrasonic welding machine created at JINR. The main features of the chamber and some characteristics of the drift tubes are described. Four such chambers with the X, Y, U, V coordinates each, containing 7168 straws in total, are designed and produced at JINR and CERN. They are installed in the vacuum volume of the NA62 setup in order to study the ultra-rare decay K+→π+vv¯ and to search for and study rare meson decays. In autumn 2014 the chambers were used for the first time for the data taking in the experimental run of the NA62 at CERN׳s SPS.

The design, construction and test of a charged particle detector made of scintillation counters read by Silicon Photomultipliers (SiPM) is described. The detector, which operates in vacuum and is used as a veto counter in the NA62 experiment at CERN, has a single channel time resolution of 1.14 ns, a spatial resolution of ∼2.5 mm and an efficiency very close to 1 for penetrating charged particles.

The branching ratio (BR) for the decay K^+ \to \pi^+\nu\bar{\nu} 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 blocks and solutions adopted for monitoring their performance, and the development of front-end electronics to allow simultaneous time and energy measurements over an extended dynamic range using the time over-threshold technique. Our results are based on test-beam data and are reproduced by a detailed Monte Carlo simulation that includes the readout chain.

The P326 experiment at the CERN SPS has been proposed with the purpose of measuring the branching ratio for the decay K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> rarrpi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> nunu macrto within ~10%. The photon veto system must provide a rejection factor of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> for pideg decays. We have explored two designs for the large-angle veto detectors, one based on scintillating tiles and the other using scintillating fibers. We have constructed a prototype module based on the fiber solution and evaluated its performance using low-energy electron beams from the Frascati Beam-Test Facility. For comparison, we have also tested a tile prototype constructed for the CKM experiment, as well as lead-glass modules from the OPAL electromagnetic barrel calorimeter. We present results on the linearity, energy resolution, and time resolution obtained with the fiber prototype, and compare the detection efficiency for electrons obtained with all three instruments.

The branching ratio (BR) for the decay K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> →π <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> νν̅ 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 dominant background from channels with final state photons, the large-angle vetoes (LAVs) must detect photons of energy as low as 200 MeV with an inefficiency of less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , as well as provide energy and time measurements with resolutions of 10% and 1 ns for 1 GeV photons. The LAV detectors make creative reuse 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 blocks and solutions adopted for monitoring their performance, and the development of front-end electronics to allow simultaneous time and energy measurements over an extended dynamic range using the time-over-threshold technique. Our results are based on test-beam data and are reproduced by a detailed Monte Carlo simulation that includes the readout chain.

The NA62 experiment at CERN SPS has been proposed with the purpose to measure the Branching Ratio for the ultrarare decay K+→ πvv. The photon veto system will have to provide a rejection better than 10-8 for π0 decays. The system is composed by several detectors. The larger ones constitute the Large Angle Veto (LAV) system, and will cover an angular region up to 50 mrad with respect to the incident beam. In order to optimize the cost/performance ratio we have tested three different technologies for the LAV system using a low energy electron beam at the LNF Beam Test Facility. A lead-scintillating fibers prototype has been built on purpose; a lead-scintillating tiles prototype was on loan by former CKM collaboration; a set of lead glass blocks from the OPAL barrel calorimeter have also been tested. We present preliminary results on detector performances and compare the three solutions.

The rare decays are excellent processes to make tests of new physics at the highest scale complementary to LHC thanks to their theoretically cleaness. The NA62 experiment at CERN SPS aims to collect of the order of 100 events in two years of data taking, keeping the background at the level of 10%. Part of the experimental apparatus has been commissioned during a technical run in 2012. The physics prospects and the status of the experiment will be reviewed after the commissioning run of 2014 and the data taking in 2015.

The NA62 low mass spectrometer consists of 7000 straw tubes operating in vacuum. The front-end electronics is directly mounted on the detector and connected by a flexible PCB. The front-end board provides the amplification, shaping, discrimination and time measurements of the analogue signals from 16 channels. After digitisation the data is sent to a VME 9U read-out board. The data, once matched with the trigger, is sent to the next step and used by the trigger level 1 algorithm. The front-end and read-out systems of the detector will be presented along with the first results of the detector performances.

TPG is the acronym for Time Projection Chamber with GEM amplification, high-granularity hexaboard read-out and FADC electronics. We have constructed a TPG read-out module, called TPG-head, with three GEM foils and a multilayer board, called hexaboard, covered with 710 000 hexagonal pads of 300 mum size. The total active area of this module is a disk of 30 cm diameter. The 710 000 pads are read by three sets of 576 strips dephased by 120 degrees. Each strip is read by a FADC channel with 100 ns sampling time. The module is mounted in a test-bed formed by a cylindrical field cage of 80 cm diameter and 150 cm length inside a solenoidal magnet that operates with a magnetic field up to B=0.7 Tesla. Tests with X-ray sources show an intrinsic spatial resolution of the order of 40 mum. The threshold for transverse momentum measurement of low energy tracks is below 0.1 MeV/c with a magnetic field of 0.07 Tesla. At 0.7 Tesla the intrinsic space point resolution of the chamber is such that the error on the measurement of the transverse momentum is DeltaP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> sime0.1 MeV/c in absence of distortions from the drift region

During my PhD course I have been involved in research activities into the frame of the NA62 experiment, which main goal is the measurement of the branching fraction B(K+ -> pi+ nu anti-nu). NA62 is a very challenging experiment due to ultra rare nature of this decay (BR is about 8e(-11)). The study of the decay K+ -> pi+ nu anti-nu is very important because it allows the first direct measurement of CKM element Vtd. Moreover it could provide signals of physics beyond Standard Model (SM) as that decay is highly sensitive to new physics. The experiment will be located at CERN experimental SPS North Area (hence the acronym NA). It is a fixed target experiment done using a unseparated 75 GeV/c beam of positive hadrons, produced by a 400 GeV/c proton beam. Positive Kaons, although being only 6% of the beam, are produced in a very abundant fashion, and will allow us to collect enough statistics to reach a about 10% relative uncertainty after a 2 years long data taking. To reach such level of uncertainty and to keep signal/background ratio below 10, the apparatus is designed in order to provide both particle identification and kinematical rejection. My work was focused on two veto subsystems with different scope, different architecture and different dimensions: the Large Angle photon Veto (or LAV) and the CHarged ANTIcounter (or CHANTI). The LAV is made of 12 different stations all along the decay region. Each station is ring shaped. The main task of LAV is to veto photons from neutral pions decay with an inefficiency lower than 10e(-4), to reduce background from K+ -> pi+ pi0. In order to choose the best technology to implement the detector we have had an intense R&D program. Three different prototypes were tested and finally a solution that uses lead glass blocks from former OPAL electromagnetic calorimeter was chosen. The prototype used to measure inefficiency was made in Naples and tested at Laboratori Nazionali di Frascati beam test facility with electrons of energy between 300 and 500 MeV/c. Unfortunately the area at CERN where blocks were stored was flooded and all blocks were involved. This major event forced a massive recovering campaign, of which I was responsible. During recovering operations many problems were found and (most of them) solved. However not all flooded blocks may be used for LAV. Part of them were damaged (9%) and an other part showed an abnormal behaviour. During the recovering operation the design of the LAV was refined and construction started. In order to reduce costs we opted for a read-out electronics based on Time over Threshold (ToT) technique. The first station out of 12 was realized and tested at CERN in June-September 2009. It was an important mile stone. The test was intended, basically, as confirmation of ToT usefulness and as check of off-line equalization procedure that each block needes to pass before being mounted. To test ToT, signals were splitted and read on one side by custom ToT electronics and from the other side by a commercial CAEN QDC, in order to produce a ToT versus charge curve. Surprisingly not a unique curve was found. After an accurate data analysis the problem was isolated and a solution proposed, consisting in changing the HV dividers of all blocks. A second module was built with new dividers and tested again at CERN. Preliminary data analysis (still going) is showing that the problem is solved and ToT can be used as read-out solution. The other item I was involved on is the CHANTI project. It is a small detector that will be placed just after last station of incoming Kaon tracking system (called Giga TracKer or GTK). GTK is made of three silicon station hit by the 800 MHz incoming beam of hadrons. About 0.3% of particles crossing the GTK undergo in inelastic collision in which the incoming hadron strongly interacts with a nuclei of GTK station producing many particles, among them pions. If inelastic events involves the third station a signal event could be mimicked if only a pion is detected. CHANTI aims to veto these events detecting the cloud of particles produced together with pion. It is made by a series of guard ring made by X and Y scintillating bars planes. Bars have a triangular shape, thus are naturally staggered. Each bar is read through a Wave Length Shifter fiber coupled to a Silicon PhotoMultiplier (SiPM). A detailed Monte Carlo was adopted to improve geometry design and to estimate the efficiency of CHANTI; moreover neutron fluence, crucial if SiPM are to be used, was estimated. Finally we designed and constructed a first full size prototype. Preliminary results about response and time resolution have been done using cosmic rays.

The NA62 experiment at CERN SPS aims at measuring-100 events of the very rare decay K+ →π +ννˉ (BR∼8.5xlO∼10). It poses stringent requirements on PID capabilities to reject the overwhelming π+π0 (63%) and Kμ2(21%) backgrounds. The photon veto system must provide a rejection factor of 10∼8 on π0 decays. As a main γ veto detector, the NA48 liquid Kripton calorimeter will be used. To have full geometrical acceptance up to 50 mr, a set of 12 veto stations should be placed along the vacuum decay tank, with an inefficiency <10∼4 in a wide energy range (200 MeV-35 GeV). Good energy resolution (∼10% at 1 GeV) for threshold definition, good time resolution (∼1 ns) to be used at the trigger level, sensitivity to MIP for calibration with muons of the beam halo are needed. A moderate segmentation in the azimuthal angle is desirable, for reducing the counting rate and providing information on the γ direction. We performed an intense R&D program on three solutions: “spaghetti” calorimeter, lead/scintillator sandwich calorimeter, and original re-use of the existing barrel of the OPAL lead-glass e.m. calorimeter. Studies have been performed at the Frascati BTF beam and all three meet the efficiency requirements. The final choice uses a peculiar radial arrangement of lead-glasses in rings. Front-end electronics has been designed to cover the tree orders of magnitude of the signal, contributing to the trigger, and integrated in the general TDAQ, while keeping low cost and simplicity. The first five full veto stations have been constructed. Two tests have been done and problems found fixed. We will discuss about R&D for the technology choice, LAV construction, test beams results and simulation performance.

The NA62 experiment at CERN aims at the very challenging task of measuring with 10% relative error the Branching Ratio of the ultra-rare decay K+→ π+v, which is expected to occur only in about 8 out of 1011 kaon decays. This will be achieved by means of an intense hadron beam, an accurate kinematical reconstruction and a redundant veto system for identifying and suppressing all spurious events. In particular, beam induced background, caused by inelastic interactions of the hadron beam with the Si based detector which measures kaon momentum (the so called Gigatracker, GTK) can mimic the signal in case only one pion is detected downstream. To suppress this background we have designed the so called CHarged ANTIcounter (CHANTI) i.e. a series of six guard counters, to be operated in vacuum and covering a wide angular region downstream the last GTK station. CHANTI must have time resolution ∼ 1 ns, must be highly efficient in detecting charged particles and must cope with rates which in the inner part can be some kHz/cm2. We have adopted a solution based on triangularly shaped scintillator bars coupled with fast wave–length shifting fibers and individually read by means of Silicon Photomultipliers (SiPM). The full scale prototype of one counter has been built and tested using a prototype front end electronic board which allows fast amplification and individual channel fine bias setting with O(mV) resolution and 0.1% stability. We show first results on the response of the detector to minimum ionizing particles as well as on its time resolution, which are well in line with the specifications.

The NA62 experiment at the CERN SPS will measure the branching ratio for the decay K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ® π <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> v <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−</sup> to within »10%. The large-angle veto (LAV) detectors must detect photons with energies as low as 200 MeV with an inefficiency of less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> . After a comprehensive series of comparative studies, NA62 decided to base the LAV system on the lead-glass block/PMT assemblies recycled from the OPAL barrel calorimeter, and a prototype veto station, complete with front-end electronics, was constructed and tested in 2009. Eleven additional stations are to be constructed before data taking begins in 2012. We describe the design, construction, and testing of the LAV system, including the recovery and mechanical adaptation of the OPAL hardware, issues related to operation in high vacuum, HV distribution, and in-situ monitoring, and especially, the design of an efficient and economical system for the readout of time and energy over an extended dynamic range.

The NA62 experiment at CERN SPS, aimed to measure ~80 events of very rare decay K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ¿ ¿+ ¿ anti-v (BR~8.5×10-10), poses stringent requirements on PID capabilities to reject the overwhelming K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿2</sub> (63%) and K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿2</sub> (21%) backgrounds. The photon veto system must provide a rejection factor of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> on ¿ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> decays. As main ¿ veto detector, the NA48 liquid Kr calorimeter will be used. To have full geometrical acceptance, a set of 12 veto stations will be placed along the vacuum decay tank, with an inefficiency <10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> in a wide energy range (50 MeV-35 GeV). Good energy resolution (~10% at 1 GeV) for threshold definition, good time resolution (~1 ns) to be used at the trigger level, sensitivity to mip, for calibration with muons of the beam halo are needed. We performed an intense R&D program on 3 solutions. Studies have been performed at the Frascati BTF beam and all 3 meet the efficiency requirements. The final choice uses a peculiar radial arrangement of lead glasses in rings. Studies on the front-end electronics are under way. The first full veto station has been constructed installed and tested at CERN.

A fast and effective algorithm for electromagnetic and hadronic shower separation has been developed for the digital sampling calorimeter of the CHARM II experiment. It is based on a generalization of the minimal spanning tree concept and can be easily applied to other existing calorimeters. In this particular application, which requires the highest efficiency for retaining electromagnetic showers, one gets, for 99% efficiency, a rejection factor of the order of 100 for hadronic showers.

TPG is the acronym for a 3D imaging gas chamber with GEM amplification, hexaboard read-out and FADC electronics. We have constructed a TPG-head with three GEM foils (30 cm diameter) and a read-out board (30 cm diameter active surface) covered with 710000 hexagonal pads of 300 /spl mu/m size. The aligned pads are connected in parallel to one strip out of three sets of 576 parallel strips (500 /spl mu/m pitch). The three sets of strips run at 120 degrees from each other and at three different depths inside the hexaboard multi-layer structure. Each strip is read by FADC electronics. The TPG-head is under initial test in a small container with a drift volume 33 mm long and of 30 cm diameter. A 150 cm long drift volume inside a 0.7 Tesla solenoidal magnetic field has been prepared by using HARP-TPC instrumentation as a test bed.

Inclusive distributions are presented for final-state ${\ensuremath{\pi}}^{0}$ and ${\ensuremath{\eta}}^{0}$ mesons produced in $\ensuremath{\gamma}p$ interactions. For photon energies from 50 to 130 GeV, both cross sections scale for fractional momenta ${x}_{F}&gt;~0.30$. The average transverse momentum for both mesons is approximately constant with energy and equal to 0.51\ifmmode\pm\else\textpm\fi{}0.05 GeV/c at large ${x}_{F}$. The $\frac{{\ensuremath{\eta}}^{0}}{{\ensuremath{\pi}}^{0}}$ ratio similarly rises from 0.07\ifmmode\pm\else\textpm\fi{}0.03 at ${x}_{F}=0.38 \mathrm{to} 0.30\ifmmode\pm\else\textpm\fi{}0.09$ at ${x}_{F}=0.90$. The ${\ensuremath{\pi}}^{0}$ distributions are in good agreement with those seen in the scattering of highly virtual incident photons.

The NA48/2 Collaboration at CERN has accumulated and analysed unprecedented statistics of rare kaon decays in the $K_{e4}$ modes: $K_{e4}(+-)$ ($K^\pm \to π^+ π^- e^\pm ν$) and $K_{e4}(00)$ ($K^\pm \to π^0 π^0 e^\pm ν$) with nearly one percent background contamination. It leads to the improved measurement of branching fractions and detailed form factor studies. New final results from the analysis of 381 $K^\pm \to π^\pm γγ$ rare decay candidates collected by the NA48/2 and NA62 experiments at CERN are presented. The results include a decay rate measurement and fits to Chiral Perturbation Theory (ChPT) description.

NA62 experiment Straw tracker frontend board serves as a gas-tight detector cover and integrates two CARIOCA chips, a low cost FPGA (Cyclon III, Altera) and a set of 400Mbit/s links to the backend. The FPGA houses 16 pairs of sub-nanosecond resolution TDCs with derandomizers and an output link serializer. Evaluation methods, including simulations, and performance results of the system in the lab and on a detector prototype are presented.

The NA62 experiment at CERN is a fixed target experiment, it is located in the north area SPS high intensity facility.It aims at a precision measurement of the ultra-rare decay K + → π + ν ν.In order to achieve this goal a low mass ( 1.8% X 0 ) spectrometer has been built to track charged kaon decay products.The system consists of 7000 straw tubes operating in vacuum.The analogic signals are shaped, amplified and discriminated by an ASIC chip (CARIOCA) mounted on the front-end board (cover) and a TDC was implemented in a FPGA.The data is sent from the cover to the Straw Readout Board (SRB) and then to the PC farm for analysis and storage.The first NA62 physics run took place in October-December 2014 and both the detector commissioning and the measured performance are presented.The goal of this presentation is to give a general overview of the system and in particular the readout scheme.The results obtained from the alignment, r-t dependence, track fit and time resolution, are described in detail.A comparison with results from GARFIELD simulations will also be presented.

The rare decays K + → π + ν ν are excellent processes to make tests of new physics at the highest scale complementary to LHC thanks to their theoretically cleaness.The NA62 experiment at CERN SPS aims to collect of the order of 100 events in two years of data taking, keeping the background at the level of 10%.Part of the experimental apparatus has been commissioned during a technical run in 2012.The physics prospects and the status of the experiment will be reviewed after the commissioning run of 2014 and the data taking in 2015.

We describe the system presently used to perform the large scale quality control of the front-end digital electronics developed by the CHARM II collaboration for fast readout of limited streamer tubes. The system is capable of localizing individual defective components and faults in the layout.

The NA62 experiment at CERN collected a large sample of charged kaon decays with a highly efficient trigger for decays into electrons in 2007. The kaon beam represents a source of tagged neutral pion decays in vacuum. A measurement of the electromagnetic transition form factor slope of the neutral pion in the time-like region from ∼1 million fully reconstructed π0 Dalitz decay is presented. The limits on dark photon production in π0 decays from the earlier kaon experiment at CERN, NA48/2, are also reported.

The NA62 experiment at CERN SPS has been proposed with the purpose to measure the Branching Ratio for the ultrarare decay K + ! + . The photon veto system will have to provide a rejection better than 10 8 for 0 decays. The system is composed by several detectors. The larger ones constitute the Large Angle Veto (LAV) system, and will cover an angular region up to 50 mrad with respect to the incident beam. In order to optimize the cost/performance ratio we have tested three dierent technologies for the LAV system using a low energy electron beam at the LNF Beam Test Facility. A lead-scintillating bers prototype has been built on purpose; a lead-scintillating tiles prototype was on loan by former CKM collaboration; a set of lead glass blocks from the OPAL barrel calorimeter have also been tested. We present preliminary results on detector performances and compare the three solutions.

Abstract The paper summarizes the ideas, letters of intent and proposals that have been put forward for the continuation of a vigorous CERN program in the field of neutrino physics. This program is focused on the problem of neutrino mass and mixing. Several options are under study to attack this problem. Short, long and intermediate baseline searches for neutrino oscillations are all being investigated.

Abstract A method for the resolution of left-right ambiguities in planar drift chambers and its application to track reconstruction in Fermilab experiment E152 are described.