Publications (353)710 Total impact
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ABSTRACT: We update the analysis of $D$ meson mixing including the latest experimental results as of January 2014. We derive constraints on the parameters $M_{12}$, $\Gamma_{12}$ and $\Phi_{12}$ that describe $D$ meson mixing using all available data, allowing for CP violation. We also provide posterior distributions for observable parameters appearing in $D$ physics.02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: The RBC and UKQCD collaborations have recently proposed a procedure for computing the K_LK_S mass difference. A necessary ingredient of this procedure is the calculation of the (nonexponential) finitevolume corrections relating the results obtained on a finite lattice to the physical values. This requires a significant extension of the techniques which were used to obtain the LellouchLuscher factor, which contains the finitevolume corrections in the evaluation of nonleptonic kaon decay amplitudes. We review the status of our study of this issue and, although a complete proof is still being developed, suggest the form of these corrections for general volumes and a strategy for taking the infinitevolume limit. The general result reduces to the known corrections in the special case when the volume is tuned so that there is a twopion state degenerate with the kaon.01/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We study matrix elements of the "chromomagnetic" operator on the lattice. This operator is contained in the strangenesschanging effective Hamiltonian which describes electroweak effects in the Standard Model and beyond. Having dimension 5, the chromomagnetic operator is characterized by a rich pattern of mixing with other operators of equal and lower dimensionality, including also non gauge invariant quantities; it is thus quite a challenge to extract from lattice simulations a clear signal for the hadronic matrix elements of this operator. We compute all relevant mixing coefficients to one loop in lattice perturbation theory; this necessitates calculating both 2point (quarkantiquark) and 3point (gluonquarkantiquark) Green's functions at nonzero quark masses. We use the twisted mass lattice formulation, with Symanzik improved gluon action. For a comprehensive presentation of our results, along with detailed explanations and a more complete list of references, we refer to our forthcoming publication [1].11/2013;  Journal of High Energy Physics 07/2013; · 5.62 Impact Factor
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ABSTRACT: We present a method to evaluate on the lattice the leading isospin breaking effects due to both the small mass difference between the up and down quarks and the QED interaction. Our proposal is applicable in principle to any QCD+QED gauge invariant hadronic observable which can be computed on the lattice. It is based on the expansion of the pathintegral in powers of the small parameters (m_d  m_u)/Lambda_{QCD} and alpha_{em}, where m_f is the renormalized quark mass and alpha_{em} the renormalized fine structure constant. In this paper we discuss in detail the general strategy of the method and the conventional, although arbitrary, separation of QCD from QED isospin breaking corrections. We obtain results for the pion mass splitting, M_{pi+}^2M_{pi0}^2= 1.44(13)(16) x 10^3 MeV^2, for the Dashen's theorem breaking parameter epsilon_{gamma}= 0.79(18)(18), for the light quark masses, [m_d  m_u](MSbar,2 GeV)= 2.39(8)(17) MeV, [m_u / m_d](MSbar,2 GeV)= 0.50(2)(3) and for the flavour symmetry breaking parameters R and Q. We also update our previous results for the QCD isospin breaking corrections to the Kl2 decay rate and for the QCD contribution to the neutronproton mass splitting.Physical review D: Particles and fields 03/2013; 87(11).  [Show abstract] [Hide abstract]
ABSTRACT: We present a precise lattice QCD determination of the bquark mass, of the B and Bs decay constants and first results for the Bmeson bag parameters. For our computation we employ the socalled ratio method and our results benefit from the use of improved interpolating operators for the Bmesons. QCD calculations are performed with Nf = 2 dynamical lightquarks at four values of the lattice spacing and the results are extrapolated to the continuum limit. The preliminary results are mb(mb) = 4.35(12) GeV for the MSbar bquark mass, fBs = 234(6) MeV and fB = 197(10) MeV for the Bmeson decay constants, BBs(mb) = 0.90(5) and BB(mb) = 0.87(5) for the Bmeson bag parameters.12/2012; 
Article: Neutral meson oscillations in the Standard Model and beyond from Nf=2 Twisted Mass Lattice QCD
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ABSTRACT: We present the ETMC results for the bag parameters describing the neutral kaon mixing in the Standard Model and beyond and preliminary results for the bag parameters controlling the short distance contributions in the D^0\bar{D}^0 oscillations. We also present preliminary results for the B_{Bd}, B_{Bs}, B_{Bs}/B_{Bd} and \xi parameter controlling B^0_\bar{B}^0 oscillations in the Standard Model employing the socalled ratio method. Using Nf=2 maximally twisted sea quarks and OsterwalderSeiler valence quarks we achieve both O(a)improvement and continuum like renormalization pattern. Simulations are performed at threevalues of the lattice spacing and several values of quark masses in the light, strange, charm region and above charm up to ~2.5m_c. Our results are extrapolated to the continuum limit and extrapolated/interpolated to the physical quark masses.11/2012;  [Show abstract] [Hide abstract]
ABSTRACT: We present a precise lattice QCD determination of the bquark mass, of the B and Bs decay constants and first preliminary results for the Bmesons bag parameter. Simulations are performed with Nf = 2 Wilson twisted mass fermions at four values of the lattice spacing and the results are extrapolated to the continuum limit. Our calculation benefits from the use of improved interpolating operators for the Bmesons and employs the socalled ratio method. The latter allows a controlled interpolation at the bquark mass between the relativistic data around and above the charm quark mass and the exactly known static limit.11/2012;  [Show abstract] [Hide abstract]
ABSTRACT: We present the first unquenched, continuum limit, lattice QCD results for the matrix elements of the operators describing neutral kaon oscillations in extensions of the Standard Model. Owing to the accuracy of our calculation on \Delta S=2 weak Hamiltonian matrix elements, we are able to provide a refined Unitarity Triangle analysis improving the bounds coming from model independent constraints on New Physics. In our nonperturbative computation we use a combination of Nf=2 maximally twisted sea quarks and OsterwalderSeiler valence quarks in order to achieve both O(a)improvement and continuumlike renormalization properties for the relevant fourfermion operators. The calculation of the renormalization constants has been performed nonperturbatively in the RIMOM scheme. Based on simulations at four values of the lattice spacing and a number of quark masses we have extrapolated/interpolated our results to the continuum limit and physical light/strange quark masses.Journal of High Energy Physics 07/2012; 2013(3). · 5.62 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We derive constraints on the parameters $M_{12}$, $\Gamma_{12}$ and $\Phi_{12}$ that describe $D$ meson mixing using all available data, allowing for CP violation. We also provide posterior distributions and predictions for observable parameters appearing in $D$ physics.Journal of High Energy Physics 06/2012; 2012(10). · 5.62 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a new method to evaluate with high precision the isospin breaking effects due to the mass difference between the up and down quarks using lattice QCD. Our proposal is applicable in principle to any hadronic observable which can be computed on the lattice. It is based on the expansion of the pathintegral in powers of the small parameter $m_d  m_u$. In this talk we discuss how to apply this method to compute the leading isospin breaking effects for several physical quantities of interest: the kaon masses, the kaon decay constants and the neutronproton mass splitting.02/2012;  [Show abstract] [Hide abstract]
ABSTRACT: We present a new method to evaluate with high precision isospin breaking effects due to the small mass difference between the up and down quarks using lattice QCD. Our proposal is applicable in principle to any hadronic observable which can be computed on the lattice. It is based on the expansion of the pathintegral in powers of the small parameter mdmu. In this paper, we apply this method to compute the leading isospin breaking effects for several physical quantities of interest: the kaon meson masses, the kaon decay constant, the form factors of semileptonic Kl3 decays and the neutronproton mass splitting.Journal of High Energy Physics 10/2011; · 5.62 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We compute the matrix elements of the electromagnetic (EM) operator (\bar{s} F{\mu \nu} \sigma{\mu \nu} d) between kaon and pion states, using lattice QCD with maximally twistedmass fermions and two flavors of dynamical quarks (Nf = 2). The operator is renormalized nonperturbatively in the RI'/MOM scheme and our simulations cover pion masses as light as 270 MeV and three values of the lattice spacing from ~ 0.07 up to ~ 0.1 fm. At the physical point our result for the corresponding tensor form factor at zeromomentum transfer is fT{K\pi}(0) = 0.417 (14_stat) (5_syst), where the systematic error does not include the effect of quenching the strange and charm quarks. Our result differs significantly from the old quenched result fT{K\pi}(0) = 0.78 (6) obtained by the SPQcdR Collaboration with pion masses above 500 MeV. We investigate the source of this difference and conclude that it is mainly related to the chiral extrapolation. We also study the tensor charge of the pion and obtain the value fT{\pi\pi}(0) = 0.195 (8_stat) (6_syst) in good agreement with, but more accurate than the result fT{\pi\pi}(0) = 0.216 (34) obtained by the QCDSF Collaboration using higher pion masses.Physical review D: Particles and fields 08/2011; 84.  [Show abstract] [Hide abstract]
ABSTRACT: We present preliminary results on the of neutral kaon oscillations in extensions of the Standard Model. Using Nf=2 maximally twisted sea quarks and OsterwalderSeiler valence quarks, we achieve both O(a)improvement and continuumlike renormalization pattern for the relevant fourfermion operators. We perform simulations at three values of the lattice spacing and extrapolate/interpolate our results to the continuum limit and physical light/strange quark mass. The calculation of the renormalization constants of the complete operator basis is performed non perturbatively in the RIMOM scheme. Comment: 7 pages, 2 figures; presented at the XXVIII International Symposium on Lattice Field Theory Villasimius, Sardinia, Italy12/2010;  [Show abstract] [Hide abstract]
ABSTRACT: We present the status of the Unitarity Triangle Analysis (UTA), within the Standard Model (SM) and beyond, with experimental and theoretical inputs updated for the ICHEP 2010 conference. Within the SM, we find that the general consistency among all the constraints leaves space only to some tension (between the UTA prediction and the experimental measurement) in BR(B > tau nu), sin(2 beta) and epsilon_K. In the UTA beyond the SM, we allow for New Physics (NP) effects in (Delta F)=2 processes. The hint of NP at the 2.9 sigma level in the B_s\bar B_s mixing turns out to be confirmed by the present update, which includes the new D0 result on the dimuon charge asymmetry but not the new CDF measurement of phi_s, being the likelihood not yet released.10/2010;  [Show abstract] [Hide abstract]
ABSTRACT: We present the summer 2012 update of the Unitarity Triangle (UT) analysis performed by the UTfit Collaboration within the Standard Model (SM) and beyond. The increased accuracy on several of the fundamental constraints is now enhancing some of the tensions amongst and within the constraint themselves. In particular, the long standing tension between exclusive and inclusive determinations of the V and V CKM matrix elements is now playing a major role. Then we present the generalisation the UT analysis to investigate new physics (NP) effects, updating the constraints on NP contributions to ΔF=2 processes. In the NP analysis, both CKM and NP parameters are fitted simultaneously to obtain the possible NP effects in any specific sector. Finally, based on the NP constraints, we derive upper bounds on the coefficients of the most general ΔF=2 effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of NP that contributes to these lowenergy effective interactions.Nuclear Physics B  Proceedings Supplements 01/2010; · 0.88 Impact Factor  01/2010;

Article: An improved Standard Model prediction of BR ( B → τ ν ) and its implications for New Physics
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ABSTRACT: The recently measured B→τν branching ratio allows to test the Standard Model by probing virtual effects of new heavy particles, such as a charged Higgs boson. The accuracy of the test is currently limited by the experimental error on BR(B→τν) and by the uncertainty on the parameters fB and Vub. The redundancy of the Unitarity Triangle fit allows to reduce the error on these parameters and thus to perform a more precise test of the Standard Model. Using the current experimental inputs, we obtain BR(B→τν)SM=(0.84±0.11)×10−4, to be compared with BR(B→τν)exp=(1.73±0.34)×10−4. The Standard Model prediction can be modified by New Physics effects in the decay amplitude as well as in the Unitarity Triangle fit. We discuss how to disentangle the two possible contributions in the case of minimal flavour violation at large tanβ and generic loopmediated New Physics. We also consider two specific models with minimal flavour violation: the TypeII Two Higgs Doublet Model and the Minimal Supersymmetric Standard Model.Physics Letters B  PHYS LETT B. 01/2010; 687(1):6169. 
Article: Global fit to CKM data (UTfit)
01/2010; 
Article: Matrix elements of the electromagnetic and chromomagnetic operators between kaon and pion states
01/2010;
Publication Stats
9k  Citations  
710.00  Total Impact Points  
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Institutions

2012

Scuola Internazionale Superiore di Studi Avanzati di Trieste
Trst, Friuli Venezia Giulia, Italy


1984–2010

Università degli Studi di Roma "La Sapienza"
 Department of Physics
Roma, Latium, Italy


2001–2005

Università Degli Studi Roma Tre
 Department of Mathematics and Physics
Roma, Latium, Italy


1988–2001

University of Southampton
 • Department of Physics and Astronomy
 • Faculty of Physical and Applied Sciences
Southampton, England, United Kingdom


1987–2001

Université ParisSud 11
 Laboratoire de Physique Théorique d'Orsay
Orsay, ÎledeFrance, France


2000

French National Centre for Scientific Research
Lutetia Parisorum, ÎledeFrance, France


1995–2000

Boston University
 Department of Physics
Boston, MA, United States


1998

Technische Universität München
 Faculty of Physics
München, Bavaria, Germany


1997–1998

Bergische Universität Wuppertal
Wuppertal, North RhineWestphalia, Germany 
Scuola Normale Superiore di Pisa
Pisa, Tuscany, Italy


1981–1998

CERN
 • Physics Department (PH)
 • Theoretical Physics Unit (TH)
Genève, Geneva, Switzerland


1985–1991

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


1989

Universidad Autónoma de Madrid
 Departamento de Física Teórica
Madrid, Madrid, Spain


1978

INFN  Istituto Nazionale di Fisica Nucleare
Frascati, Latium, Italy
