F. Marchetto

Study of the chi(1) and chi(2) charmonium states formed in anti-p p annihilations

We report on a study of the χ1(3P1) and χ2(3P2) states of charmonium formed in antiproton-proton annihilations. An energy scan through the resonances, performed with a very narrow momentum-band beam of antiprotons intersecting a hydrogen jet target, enables us to perform very precise measurements of the mass and the total width of the two resonances. From a sample of 513 χ1 and 585 χ2 events we find Mχ1 = (3510.53±0.13) MeV/c2, Mχ2 = (3556.15±0.14) MeV/c2, Γχ1 = (0.88±0.14) MeV and Γχ2 = (1.98±0.18) MeV. From our measurement of the quantity Γ(R → pp) × BR(R → Jψ → e+ e−), using known branching ratios, we obtain Λ(χ1 → pp) = (69±13) eV and Λ(χ2 → pp) = (180±31) eV.

A pixel front-end ASIC in 0.13 μm CMOS for the NA62 experiment with on pixel 100 ps Time-to-Digital Converter

The paper describes the design of a front-end chip for hybrid pixel detectors optimized for good timing resolution (200 ps rms) and high event rate (150 kHz per pixel). Each channel consists of a fast transimpedance amplifier with 5 ns peaking time, a constant fraction discriminator (CFD), and a Time-to-Digital Converter (TDC). In order to cope with the rate requirement, a multi-event buffering scheme employing both analog and digital pipelines is implemented in each cell. This development is part of the R&D activity for the silicon tracker of the NA62 experiment at CERN. The architecture of the chip and the design of the critical building blocks are discussed in the paper.

Precision measurements of the total and partial widths of the ψ (2 S) charmonium meson with a new complementary-scan technique in over(p, ̄) p annihilations

We present new precision measurements of the {Psi}(2S) total and partial widths from excitation curves obtained in antiproton-proton annihilations by Fermilab experiment E835 at the Antiproton Accumulator in the year 2000. A new technique of complementary scans was developed to study narrow resonances with stochastically cooled antiproton beams. It relies on precise revolution-frequency and orbit-length measurements, while making the analysis of the excitation curve almost independent of machine lattice parameters. For the {Psi}(2S) meson, by studying the processes {bar p}p {yields} e{sup +}e{sup -} and {bar p}p {yields} J/{Psi} + X {yields} e{sup +}e{sup -} + X, we measure the width {Gamma} = 290 {+-} 25(sta) {+-} 4(sys) keV and the combination of partial widths {Gamma}{sub e{sup +}e{sup -}}{Gamma}{sub {bar p}p}/{Gamma} = 579 {+-} 38(sta) {+-} 36(sys) meV, which represent the most precise measurements to date.

Measurement of the resonance parameters of the χ1(13P1) and χ2(13P2) states of charmonium formed in antiproton–proton annihilations

The authors have studied the {sup 3}P{sub J} ({chi}{sub e}) states of charmonium in formation by antiproton-proton annihilations in experiment E835 at the Fermilab Antiproton Source. The authors report new measurements of the mass, width, and B({chi}{sub cJ} {yields} {bar p}p) x {Lambda}({chi}{sub eJ} {yields} J/{psi} + anything) for the {chi}{sub c1} and {chi}{sub c2} by means of the inclusive reaction {bar p}p {yields} {chi}{sub cJ} {yields} J/{psi} + anything {yields} (e{sup +}e{sup -}) + anything. Using the subsample of events where {chi}{sub cJ} {yields} {gamma} + J/{psi} {yields} {gamma} + (e{sup +}e{sup -}) is fully reconstructed, we derive B({chi}{sub cJ} {yields} {bar p}p) x {Lambda}({chi}{sub cJ} {yields} J/{psi} + {gamma}). They summarize the results of the E760 (updated) and E835 measurements of mass, width and B({chi}{sub cJ} {yields} {bar p}p){Lambda}({chi}{sub cJ} {yields} J/{psi} + {gamma}) (J = 0,1,2) and discuss the significance of these measurements.

Experimental results from a pixel front-end for the NA62 experiment with on pixel constant fraction discriminator and 100 ps Time to Digital Converter

The paper presents test results of a front-end ASIC developed for fast timing applications with silicon pixel detectors. Implemented in a 0.13 μm CMOS process, the prototype integrates 107 read-out cells. In an area of 300 μm × 300 μm each cell incorporates a fast transimpedance amplifier with 3 ns peaking time, a Constant Fraction Discriminator (CFD) and a Time to Digital Converter (TDC). The analog front-end is optimized for signals from 1 fC to 10 fC and dissipates lmW from a 1.2 V supply. Electrical tests of the key building blocks and system level aspects are discussed in the paper.

Hadrontherapy: An open source, Geant4-based application for proton-ion therapy studies

Hadrontherapy is an open source application based on the Geant4 Monte Carlo libraries. It can be downloaded with the Geant4 official code and can be found in the category of the advanced examples (

Electron production by 4.0 GeV/c π+p interactions

G4Install/examples/advanced folder of the Geant4 distribution). Since its original version, released in 2004, Hadrontherapy permitted the simulation of a typical proton therapy beam line, together with all it elements (collimators, scattering systems, etc.) and the calculation of the corresponding dose distribution curves in water and other materials. In this paper we will report on the newest development and improvement of Hadrontherapy as it will be released in the Geant4 9.3 version. The new version of application will furnish a set of tools useful for Users interested in studies related to proton/ion therapy. The new version of Hadrontherapy will permit, in fact, the transport of carbon beams, using the state-of-art of the Geant4 electromagnetic and hadronic models, the calculation of some basic parameters like stopping powers, or the possibility to easily change the geometrical configuration for the simulation of typical nuclear physics experiment of interest in the hadrontherapy field. Other capabilities are inserted in the new Hadrontherapy version even if not all are reported in this paper. For more information the reader can refer to the on-line manual of Hadrontherapy that can be found inside the Geant4 official website (www.cern.ch/geant4).

Development of the ASICs for the NA62 pixel gigatracker

Abstract We have investigated electron production in 4.0 GeV/ c π + pinteractions. Limits to direct electron pair production are measured and an example of ϱ 0 or ω 0 decay to e + e − is observed. The ratio of the number of singly produced electrons to the total number of charged pions is less than 6 × 10 -5 (at the 95% confidence level).

Pixel read-out architectures for the NA62 gigatracker

We present the ASIC development for the readout electronics of the Gigatracker pixel detector of NA62. Specifications of this detector are challenging in terms of timing precision with a hit time stamp accuracy of 100 ps and a peak hit rate of 50 Mhits/cm/s. A timing precision and hit rate are more than one order of magnitude faster than pixel LHC readout ASIC. The research for pixel cell design and the readout architectures are following two approaches, which are presented and discussed in this paper. Presently demonstrator prototypes are under development and SPICE simulation results of the frontend, the readout strategy and and the pixelcolumn are also presented and discussed.

The electro-mechanical integration of the NA62 GigaTracker time tagging pixel detector

Beam particles in NA62 experiment are measured with a Si-pixel sensor having a size of 300 μm x 300 μm and a time resolution of 150 ps (rms). To meet the timing requirement an adequate strategy to compensate the discriminator time-walk must be implemented and an R&D effort investigating two different options is ongoing. In this presentation we describe the two different approaches. One is based on the use of a constant-fraction discriminator followed by an on-pixel TDC. The other one is based on the use of a Time-over-Threshold circuit followed by a TDC shared by a group of pixels. The global architectures of both the front-end ASIC will be discussed. I. THE GIGATRACKER SYSTEM The aim of the proposed NA62 experiment at the CERN SPS is to study the very rare decay of the charged K meson into a pion and neutrino-antineutrino pair. One of the key components of NA62 will be the GigaTracker, which consists of three matrices of Si-pixel stations, each covering a sensitive area of 60 mm x 27 mm. Each pixel is 300 μm x 300 μm [1]. The GigaTracker is designed to measure the beam particle trajectory with a space resolution of 100 μm (rms) and a timing accuracy of 150 ps (rms). In order to reconstruct the momentum of the beam particles a system of four dipoles, A1...A4 in Fig.1, provides the momentum selection followed by the beam recombination. The timing resolution of 150 ps (rms) is an unusual requirement for a traditional pixel detector and none of the existing systems has such a capability. Other challenging aspects are due to the high radiation operational environment and the very low material budget restraint (0.5% X0 per station, sensor thickness 200 μm, read-out chip thickness 150 μm). Figure 1: GigaTracker system Each silicon sensor will be read-out by 10 front-end ASICs, with 45x40 read-out cells each. The 10 read-out chips will be bump-bonded to the pixels, so only one side of the chip will be used for external connections (wire bonding pads in Fig. 2). Figure 2: Sensor and read-out chips The particle rate, which is higher in the central part of the sensor, is estimated to be ~1.5 MHz/mm maximum, which corresponds to 130 MHz per chip and 140 kHz per