Publications (200)339.03 Total impact

Article: Recent NA48/2 and NA62 results
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ABSTRACT: The NA48/2 Collaboration at CERN has accumulated and analysed unprecedented statistics of rare kaon decays in the $K_{e4}$ modes: $K_{e4}(+)$ ($K^\pm \to \pi^+ \pi^ e^\pm \nu$) and $K_{e4}(00)$ ($K^\pm \to \pi^0 \pi^0 e^\pm \nu$) 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 $K^\pm \to \pi^\pm \gamma \gamma$ 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.08/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Using the full data set of the NA48/2 experiment, the decay K+ > pi+ e+ e gamma is observed for the first time, selecting 120 candidates with 7.3 + 1.7 estimated background events. With K+ > pi+ pi0D as normalisation channel, the branching ratio is determined in a modelindependent way to be Br(K+ > pi+ e+ e gamma, m_eegamma > 260 MeV/c^2) = (1.19 + 0.12_stat + 0.04_syst) x 10^8. This measured value and the spectrum of the e+ e gamma invariant mass allow a comparison with predictions of Chiral Perturbation Theory.07/2013;  Physics Letters B. 08/2012; 715(s 1–3):105–115.
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ABSTRACT: A sample of more than one million (Ke4) decay candidates with less than one percent background contamination has been collected by the NA48/2 experiment at the CERN SPS in 20032004, allowing a detailed study of the decay properties. The branching ratio, inclusive of Ke4 decays, is measured to be with a total relative error of 0.8%. This measurement complements the study of S and Pwave hadronic form factors by assigning absolute values to the relative hadronic form factors obtained earlier in a simultaneous analysis of the ππ scattering lengths conducted on the same data sample. The overall form factor normalization is obtained with a total relative precision of 0.6%. © 2012 Elsevier B.V.Physics Letters, Section B: Nuclear, Elementary Particle and HighEnergy Physics. 01/2012; 715(13):105115.  [Show abstract] [Hide abstract]
ABSTRACT: A sample of 7253 K{sup {+}} {yields} {pi}{sup {+}}e{sup +}e{sup }({gamma}) decay candidates with 1.0% background contamination has been collected by the NA 48/2 experiment at the CERN SPS, which allowed a precise measurement of the decay properties. The branching ratio in the full kinematic range was measured to be BR = (3.11 {+} 0.12) x 10{sup 7}, where the uncertainty includes also the model dependence. The shape of the form factor W(z), where z = (M{sub ee}/M{sub K}){sup 2}, was parameterized according to several models, and, in particular, the slope {delta} of the linear form factor W(z) = W{sub 0}(1 + {delta}z) was determined to be {delta} = 2.32 {+} 0.18. A possible CP violating asymmetry of K{sup +} and K{sup } decay widths was investigated, and a conservative upper limit of 2.1 x 10{sup 2} at 90% CL was established.11/2011; 677(5). 
Article: THE SOFTWARE OF THE APE100 PROCESSOR
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ABSTRACT: We describe the software environment available for the APE100 parallel processor. We discuss the parallel programming language that we have defined for APE100 and its optimizing compiler. We then describe the operating system that allows to control APE100 from a host computer.International Journal of Modern Physics C 11/2011; 04(05). · 0.62 Impact Factor  Physics Letters B. 02/2011; 697(2):107–115.

Article: Flavor physics in the quark sector
Physics Reports. 09/2010; 494(s 3–4):197–414.  [Show abstract] [Hide abstract]
ABSTRACT: As first observed by the NA48/2 experiment at the CERN SPS, the $\p0p0$ invariant mass (M00) distribution from $\kcnn$ decay shows a cusplike anomaly at M00=2m+, where m+ is the charged pion mass. An analysis to extract the pi pi scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively, has been recently reported. In the present work the Dalitz plot of this decay is fitted to a new empirical parameterization suitable for practical purposes, such as Monte Carlo simulations of K+ > pi+ pi0 pi0 decays. Comment: 9 pages, 3 figures.04/2010;  Physics Letters B. 03/2010; 686(s 2–3):101–108.
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ABSTRACT: As first observed by the NA48/2 experiment at the CERN SPS, the π0π0 invariant mass (M00) distribution from K±→π±π0π0 decay shows a cusplike anomaly at M00=2m+, where m+ is the charged pion mass. An analysis to extract the ππ scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively, has been recently reported. In the present work the Dalitz plot of this decay is fitted to a new empirical parameterization suitable for practical purposes, such as Monte Carlo simulations of K±→π±π0π0 decays.Physics Letters B. 01/2010;  [Show abstract] [Hide abstract]
ABSTRACT: We report results from the analysis of the $\mbox {$\mbox { ($\mbox {$\mbox {) decay by the NA48/2 collaboration at the CERN SPS, based on the total statistics of 1.13 million decays collected in 2003–2004. The hadronic form factors in the S and Pwave and their variation with energy are obtained. The phase difference between the S and Pwave states of the ππ system is accurately measured and allows a precise determination of $\mbox {$\mbox { and $\mbox {$\mbox {, the I = 0 and I = 2 Swave ππ scattering lengths: $\mbox {$\mbox {. Combination of this result with the other NA48/2 measurement obtained in the study of $\mbox {$\mbox { decays brings an improved determination of $\mbox {$\mbox { and the first precise experimental measurement of $\mbox {$\mbox {, providing a stringent test of Chiral Perturbation Theory predictions and lattice QCD calculations. Using constraints based on analyticity and chiral symmetry, even more precise values are obtained: $\mbox {$\mbox { and $\mbox {$\mbox {.European Physical Journal C 01/2010; 70(3):635657. · 5.25 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report on the measurement of the direct emission (DE) and interference (INT) terms of the $K\pm > \pi \pm \pi^0 \gamma$ decay by the NA48/2 experiment at the CERN SPS. From the data collected during 2003 and 2004 about 600k such decay candidates have been selected. The relative amounts of DE and INT with respect to the internal bremsstrahlung (IB) contribution have been measured in the range 0<T*\pi<80 MeV: Frac_{DE} (0<T*\pi<80 MeV) = (3.32\pm 0.15_{stat} \pm 0.14_{sys})x10^{2} Frac_{INT} (0<T*\pi<80 MeV) = ( 2.35\pm 0.35_{stat} \pm 0.39_{sys})x10^{2}, where T*pi is the kinetic energy of the charged pion in the kaon rest frame. This is the first observation of an interference term in T*\pi decays. In addition, a limit on the CP violating asymmetry in the K^+ and K^ branching ratios for this channel has been determined to be less than 1.5x10^{3} at 90% confidence level.01/2010;  [Show abstract] [Hide abstract]
ABSTRACT: As first observed by the NA48/2 experiment at the CERN SPS, the π0π0 invariant mass (M00) distribution from K±→π±π0π0 decay shows a cusplike anomaly at M00=2m+, where m+ is the charged pion mass. An analysis to extract the ππ scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively, has been recently reported. In the present work the Dalitz plot of this decay is fitted to a new empirical parameterization suitable for practical purposes, such as Monte Carlo simulations of K±→π±π0π0 decays.Physics Letters B  PHYS LETT B. 01/2010; 686(2):101108.  [Show abstract] [Hide abstract]
ABSTRACT: We report on the measurement of the direct emission (DE) and interference (INT) terms of the K ±→π ± π 0 γ decay by the NA48/2 experiment at the CERN SPS. From the data collected during 2003 and 2004 about 600k such decay candidates have been selected. The relative amounts of DE and INT with respect to the internal bremsstrahlung (IB) contribution have been measured in the range MeV: where is the kinetic energy of the charged pion in the kaon rest frame. This is the first observation of an interference term in K ±→π ± π 0 γ decays, thus allowing the normalised electric and magnetic amplitudes to be measured, giving X E =(−24±6) GeV−4, and X M =(254±9) GeV−4. In addition, a limit on the CP violating asymmetry in the K + and K − branching ratios for this channel has been determined to be less than 1.5×10−3 at 90% confidence level.European Physical Journal C 01/2010; · 5.25 Impact Factor 
Article: Flavor Physics in the Quark Sector
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ABSTRACT: One of the major challenges of particle physics has been to gain an indepth understanding of the role of quark flavor and measurements and theoretical interpretations of their results have advanced tremendously: apart from masses and quantum numbers of flavor particles, there now exist detailed measurements of the characteristics of their interactions allowing stringent tests of Standard Model predictions. Among the most interesting phenomena of flavor physics is the violation of the CP symmetry that has been subtle and difficult to explore. Till early 1990s observations of CP violation were confined to neutral $K$ mesons, but since then a large number of CPviolating processes have been studied in detail in neutral $B$ mesons. In parallel, measurements of the couplings of the heavy quarks and the dynamics for their decays in large samples of $K, D$, and $B$ mesons have been greatly improved in accuracy and the results are being used as probes in the search for deviations from the Standard Model. In the near future, there will be a transition from the current to a new generation of experiments, thus a review of the status of quark flavor physics is timely. This report summarizes the results of the current generation of experiments that is about to be completed and it confronts these results with the theoretical understanding of the field. Comment: Report of the CKM workshop, Rome 913th Sep. 2008, 340 pages, 106 postscript figures, submitted to Phys. Repts07/2009;  Physics Letters B. 06/2009; 677(5):246–254.
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ABSTRACT: A sample of 7253 K>piee(gamma) decay candidates with 1.0% background contamination has been collected by the NA48/2 experiment at the CERN SPS, which allowed a precise measurement of the decay properties. The branching ratio in the full kinematic range was measured to be BR=(3.11±0.12)×10, where the uncertainty includes also the model dependence. The shape of the form factor W(z), where z=M, was parameterized according to several models, and, in particular, the slope delta of the linear form factor W(z)=W(1+deltaz) was determined to be delta=2.32±0.18. A possible CP violating asymmetry of K and K decay widths was investigated, and a conservative upper limit of 2.1×10 at 90% CL was established.Physics Letters B  PHYS LETT B. 01/2009; 677:246254. 
Article: Determination of the Swave pi pi scattering lengths from a study of K ±> pi ± pi 0 pi 0 decays
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ABSTRACT: We report the results from a study of the full sample of ˜6.031×107 K ±> pi ± pi 0 pi 0 decays recorded by the NA48/2 experiment at the CERN SPS. As first observed in this experiment, the pi 0 pi 0 invariant mass ( M 00) distribution shows a cusplike anomaly in the region around M 00=2 m +, where m + is the charged pion mass. This anomaly has been interpreted as an effect due mainly to the final state charge exchange scattering process pi + pi > pi 0 pi 0 in K ±> pi ± pi + pi  decay. Fits to the M 00 distribution using two different theoretical formulations provide the presently most precise determination of a 0 a 2, the difference between the pi pi Swave scattering lengths in the isospin I=0 and I=2 states. Higherorder pi pi rescattering terms, included in the two formulations, allow also an independent, though less precise, determination of a 2.European Physical Journal C 01/2009; 64:589608. · 5.25 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Bird flocking is a striking example of collective animal behaviour. A vivid illustration of this phenomenon is provided by the aerial display of vast flocks of starlings gathering at dusk over the roost and swirling with extraordinary spatial coherence. Both the evolutionary justification and the mechanistic laws of flocking are poorly understood, arguably because of a lack of data on large flocks. Here, we report a quantitative study of aerial display. We measured the individual threedimensional positions in compact flocks of up to 2700 birds. We investigated the main features of the flock as a whole  shape, movement, density and structure  and discuss these as emergent attributes of the grouping phenomenon. We find that flocks are relatively thin, with variable sizes, but constant proportions. They tend to slide parallel to the ground and, during turns, their orientation changes with respect to the direction of motion. Individual birds keep a minimum distance from each other that is comparable to their wingspan. The density within the aggregations is nonhomogeneous, as birds are packed more tightly at the border compared to the centre of the flock. These results constitute the first set of largescale data on threedimensional animal aggregations. Current models and theories of collective animal behaviour can now be tested against these results.03/2008;
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4k  Citations  
339.03  Total Impact Points  
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Institutions

1967–2010

CERN
 Physics Department (PH)
Genève, Geneva, Switzerland 
Istituto Superiore di Sanità
Roma, Latium, Italy


1994–2005

Sapienza University of Rome
 Department of Physics
Roma, Latium, Italy


2003

University of Chicago
 Enrico Fermi Institute
Chicago, IL, United States


1995–1997

ENEA
Roma, Latium, Italy


1960–1995

University of Rome Tor Vergata
 Dipartimento di Fisica
Roma, Latium, Italy


1959–1988

INFN  Istituto Nazionale di Fisica Nucleare
Frascati, Latium, Italy


1987

The Rockefeller University
New York City, New York, United States


1982

Università degli Studi del Sannio
Benevento, Campania, Italy


1978

Université ParisSud 11
Orsay, ÎledeFrance, France 
French National Centre for Scientific Research
Lutetia Parisorum, ÎledeFrance, France


1977

Ecole Normale Supérieure de Paris
 Laboratoire de Physique Théorique
Paris, IledeFrance, France


1962–1971

Università Degli Studi Roma Tre
Roma, Latium, Italy
