Publications (245)434.22 Total impact
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ABSTRACT: The Chromomagnetic operator (CMO) mixes with a large number of operators under renormalization. We identify which operators can mix with the CMO, at the quantum level. Even in dimensional regularization (DR), which has the simplest mixing pattern, the CMO mixes with a total of 9 other operators, forming a basis of dimensionfive, Lorentz scalar operators with the same flavor content as the CMO. Among them, there are also gauge noninvariant operators; these are BRST invariant and vanish by the equations of motion, as required by renormalization theory. On the other hand using a lattice regularization further operators with $d \leq 5$ will mix; choosing the lattice action in a manner as to preserve certain discrete symmetries, a minimul set of 3 additional operators (all with $d<5$) will appear. In order to compute all relevant mixing coefficients, we calculate the quarkantiquark (2pt) and the quarkantiquarkgluon (3pt) Green's functions of the CMO at nonzero quark masses. These calculations were performed in the continuum (dimensional regularization) and on the lattice using the maximally twisted mass fermion action and the Symanzik improved gluon action. In parallel, nonperturbative measurements of the $K\pi$ matrix element are being performed in simulations with 4 dynamical ($N_f = 2+1+1$) twisted mass fermions and the Iwasaki improved gluon action.12/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present preliminary results of the first lattice QCD calculation of the K > pi matrix elements of the chromomagnetic operator O_{CM}=g sbar sigma_{munu} G_{munu} d, which appears in the effective Hamiltonian describing Delta S=1 transitions in and beyond the Standard Model. Having dimension 5, the chromomagnetic operator is characterized by a rich pattern of mixing with operators of equal and lower dimensionality. The multiplicative renormalization factor as well as the mixing coefficients with the operators of equal dimension have been computed at oneloop in perturbation theory. The power divergent coefficients controlling the mixing with operators of lower dimension have been computed nonperturbatively, by imposing suitable subtraction conditions. The numerical simulations have been carried out using the gauge field configurations produced by the European Twisted Mass Collaboration with N_f=2+1+1 dynamical quarks at three values of the lattice spacing. Our preliminary result for the Bparameter of the chromomagnetic operator is B_{CMO}=0.29(11), which can be compared with the estimate B_{CMO}~14 currently used in phenomenological analyses.12/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present the outcomes of a very recent investigation of the decay constants of nonstrange and strange heavylight beauty vector mesons, with special emphasis on the ratio of any such decay constant to the decay constant of the corresponding pseudoscalar meson, by means of Boreltransformed QCD sum rules. Our results suggest that both these ratios are below unity.11/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present a lattice QCD calculation of the pseudoscalar decay constants fK, fD and fDs performed using the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 + 1 dynamical quarks, which include in the sea, besides two light mass degenerate quarks, also the strange and charm quarks with masses close to their values in the real world. The simulations are based on a unitary setup for the two light massdegenerate quarks and on a mixed action approach for the strange and charm quarks. We use data simulated at three different values of the lattice spacing in the range 0.06  0.09 fm and at pion masses in the range 210  450 MeV. Our main results are: fK+ / fpi+ = 1.183 (16), fK+ = 154.3 (2.0) MeV, which incorporate the leading strong isospin breaking correction due to the up and downquark mass difference, and fK = 155.0 (1.9) MeV, fD = 207.4 (3.8) MeV, fDs = 247.2 (4.1) MeV, fDs / fD = 1.192 (22) and (fD_s / fD) / (fK / fpi) = 1.003 (14) obtained in the isospin symmetric limit of QCD. Combined with the experimental measurements of the leptonic decay rates of kaon, pion, D and Dsmesons our results lead to the following determination of the CKM matrix elements: Vus = 0.2271 (29), Vcd = 0.2221 (67) and Vcs = 1.014 (24). Using the latest value of Vud from superallowed nuclear beta decays the unitarity of the first row of the CKM matrix is fulfilled at the permille level.11/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We discuss a lattice QCD computation of the $B$meson decay constants by the ETM collaboration where suitable ratios allow to reach the bottom quark sector by combining simulations around the charmquark mass with an exactly known static limit. The different steps involved in this ratio method are discussed together with an account of the assessment of various systematic effects. A comparison of results from simulations with two and four flavour dynamical quarks is presented.11/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Updated predictions for the decay constants of the D, Ds, B and Bs mesons obtained from Borel QCD sum rules for heavylight currents are presented and compared with the recent lattice averages performed by the Flavor Lattice Averaging Group. An excellent agreement is obtained in the charm sector, while some tension is observed in the bottom sector. Moreover, available lattice and QCD sumrule calculations of the decay constants of the vector D*, Ds*, B* and Bs* mesons are compared. Again some tension in the bottom sector is observed.11/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present a lattice QCD determination of the vector form factor of the kaon semileptonic decay K > pi l nu which is relevant for the extraction of the CKM matrix element V_{us} from experimental data. Our result is based on the gauge configurations produced by the European Twisted Mass Collaboration with N_f=2+1+1 dynamical fermions. We simulated at three different values of the lattice spacing and with pion masses as small as 210 MeV. Our preliminary estimate for the vector form factor at zero momentum transfer is f_+(0)=0.9683(65), where the uncertainty is both statistical and systematic. By combining our result with the experimental value of f_+(0)V_{us} we obtain V_{us}=0.2234(16), which satisfies the unitarity constraint of the Standard Model at the permille level.11/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Within the realm of QCD sum rules, one of the most important areas of application of this nonperturbative approach is the prediction of the decay constants of heavy mesons. However, in spite of the fact that, indisputably, the adopted techniques are, of course, very similar, we encounter rather dissimilar challenges, or obstacles, when extracting from twopoint correlators of appropriate heavylight currents interpolating the mesons, the characteristics of charmed mesons with different spin. In view of this, it seems worthwhile to us to revisit this issue for the case of charmed pseudoscalar mesons $D_{(s)}$ and vector mesons $D^*_{(s)}.$11/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present precision lattice calculations of the pseudoscalar decay constants of the charmed sector as well as determinations of the bottom quark mass and its ratio to the charm quark mass. We employ Nf=2+1+1 dynamical quark gauge configurations generated by the European Twisted Mass Collaboration, using data at three values of the lattice spacing and pion masses as low as 210 MeV. Strange and charm sea quark masses are close to their physical values.11/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the vector form factor relevant for the $K_{\ell 3}$ semileptonic decay using maximally twistedmass fermions with 4 dynamical flavours ($N_f=2+1+1$). Our simulations feature pion masses ranging from $210$ MeV to approximately $450$ MeV and lattice spacing values as small as $0.06$fm. Our main result for the vector form factor at zero 4momentum transfer is $f_+(0)=0.9683(65)$ where the uncertainty is both statistical and systematic. By combining our result with the experimental value of $f_+(0)V_{us}$ we obtain $V_{us}=0.2234(16)$, which satisfies the unitarity constraint of the Standard Model at the permille level.10/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Our recently completed analysis of the decay constants of both pseudoscalar and vector beauty mesons reveals that in the bottomquark sector two specific features of the sumrule predictions show up: (i) For the input value of the bottomquark mass in the $\overline{\rm MS}$ scheme $\overline{m}_b(\overline{m}_b)\approx4.18\;\mbox{GeV},$ the sumrule result $f_B\approx210$$220\;\mbox{MeV}$ for the $B$ meson decay constant is substantially larger than the recent latticeQCD finding $f_B\approx190\;\mbox{MeV}.$ Requiring QCD sum rules to reproduce the latticeQCD value of $f_B$ yields a significantly larger $b$quark mass: $\overline{m}_b(\overline{m}_b)=4.247\;\mbox{GeV}.$ (ii) Whereas QCD sumrule predictions for the charmedmeson decay constants $f_D,$ $f_{D_s},$ $f_{D^*}$ and $f_{D_s^*}$ are practically independent of the choice of renormalization scale, in the beauty sector the results for the decay constants  and especially for the ratio $f_{B^*}/f_B$  prove to be very sensitive to the specific scale setting.10/2014; 
Article: Charmed Pseudoscalar and Vector Mesons: a Comprehensive QCD SumRule View of Their Decay Constants
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ABSTRACT: In spite of undeniable similarities of the applied techniques, somewhat different challenges are encountered when extracting, from QCD sum rules derived from twopoint correlators of appropriate interpolating heavylight quark currents, the decay constants of charmed mesons of pseudoscalar nature, on the one hand, or of vector nature, on the other hand. This observation justifies a rather careful reassessment of the corresponding results.07/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present the first unquenched lattice QCD results for the bag parameters controlling the short distance contribution to D meson oscillations in the Standard Model and beyond. We have used the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 dynamical quarks, at four lattice spacings and light meson masses in the range 280500 MeV. Renormalization is carried out nonperturbatively with the RIMOM method. The bagparameter results have been used to constrain New Physics effects in DDbar mixing, to put a lower bound to the generic New Physics scale and to constrain offdiagonal squark mass terms for TeVscale Supersymmetry.03/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present a lattice QCD calculation of the up, down, strange and charm quark masses performed using the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 + 1 dynamical quarks, which include in the sea, besides two light mass degenerate quarks, also the strange and charm quarks with masses close to their physical values. The simulations are based on a unitary setup for the two light quarks and on a mixed action approach for the strange and charm quarks. The analysis uses data at three values of the lattice spacing and pion masses in the range 210  450 MeV, allowing for accurate continuum limit and controlled chiral extrapolation. The quark mass renormalization is carried out nonperturbatively using the RIMOM method. The results for the quark masses converted to the bar{MS} scheme are: mud(2 GeV) = 3.70(17) MeV, ms(2 GeV) = 99.6(4.1) MeV and mc(mc) = 1.348(42) GeV. We obtain also the quark mass ratios ms/mud = 26.66(32) and mc/ms = 11.62(16). By studying the mass splitting between the neutral and charged kaons and using available lattice results for the electromagnetic contributions, we evaluate mu/md = 0.470(56), leading to mu = 2.36(24) MeV and md = 5.03(26) MeV.Nuclear Physics B. 03/2014; 887. 
Dataset: FLAG Review 2011
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ABSTRACT: We present a sumrule calculation of the decay constants of the charmed vector mesons D⁎D⁎ and Ds⁎ from the twopoint correlator of vector currents. First, we show that the perturbative expansion in terms of the pole mass exhibits no sign of convergence whereas the reorganization of this expansion in terms of the MS¯ mass leads to a distinct hierarchy. Second, making use of the operator product expansion in terms of the MS¯ mass, we determine the decay constants of the D⁎D⁎ and Ds⁎ mesons with an emphasis on the uncertainties in these theoretically predicted quantities related both to the input QCD parameters and to the limited accuracy of the method of sum rules. Our results are fD⁎=(252.2±22.3OPE±4syst) MeVfD⁎=(252.2±22.3OPE±4syst) MeV and fDs⁎=(305.5±26.8OPE±5syst) MeV. For the ratios of the vectortopseudoscalar decay constants we report fD⁎/fD=1.221±0.080OPE±0.008systfD⁎/fD=1.221±0.080OPE±0.008syst and fDs⁎/fDs=1.241±0.057OPE±0.007syst.Physics Letters B. 01/2014; 735:12–18.  [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;  [Show abstract] [Hide abstract]
ABSTRACT: We present a lattice QCD calculation of the pseudoscalar decay constants $f_K$, $f_D$ and $f_{D_s}$ performed by the European Twisted Mass Collaboration with $N_f = 2 + 1 + 1$ dynamical fermions. We simulated at three different values of the lattice spacing, the smallest being approximately $0.06fm$, and with pion masses as small as $210$MeV. Our main results are: $f_{K^+}/f_{\pi^+}=1.183(17)$, $f_{K^+}=154.4(2.1)$MeV, $f_{D_s}=242.1(8.3)$MeV, $f_D=201.9(8.0)$MeV, $f_{D_s}/f_D=1.199(25)$ and $(f_{D_s}/f_D) / (f_K/f_\pi) = 1.005(15)$.11/2013;  [Show abstract] [Hide abstract]
ABSTRACT: We present a lattice QCD determination of the average updown, strange and charm quark masses based on simulations performed by the European Twisted Mass Collaboration with $N_f = 2 + 1 + 1$ dynamical fermions. We simulated at three different values of the lattice spacing, the smallest being approximately $0.06fm$, and with pion masses as small as $210 \text{MeV}$. Our results are: $m_{ud}(2\text{GeV})=3.70(17)\text{MeV}$, $m_s(2\text{GeV})=99.2(3.9)\text{MeV}$, $m_c(m_c)=1.350(49)\text{GeV}$, $m_s/m_{ud}=26.64(30)$ and $m_c/m_s=11.65(12)$.11/2013;  [Show abstract] [Hide abstract]
ABSTRACT: We present a lattice QCD determination of the $b$quark mass and of the $f_{B_s}$ and $f_B$ decay constants performed with $N_f = 2 + 1 + 1$ twisted mass Wilson fermions. We have used simulations at three values of the lattice spacing generated by ETMC with pion masses ranging from 210 to 440 MeV. To obtain physical quantities we performed a combined chiral and continuum limit and an extrapolation in the heavy quark mass from the charm to the $b$quark region using suitable ratios calculated at nearby heavyquark masses having an exactly known static limit. Our results are: $m_b(m_b) = 4.29 (13)$ GeV, $f_B = 196 (9)$ MeV, $f_{B_s} = 235 (9)$ MeV, $f_{B_s} / f_B = 1.201 (25)$, $(f_{B_s}/f_B)/(f_K/f_\pi) = 1.007 (16)$ and $(f_{B_s}/f_B)/(f_{D_s}/f_D) = 1.008 (13)$.11/2013;
Publication Stats
3k  Citations  
434.22  Total Impact Points  
Top Journals
Institutions

2005–2014

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


2011

Austrian Academy of Sciences
 Institut für Hochenergiephysik
Mondsee, Upper Austria, Austria


2010

University of Vienna
 Fakultät für Physik
Wien, Vienna, Austria 
HumboldtUniversität zu Berlin
 Department of Physics
Berlín, Berlin, Germany


1998–2010

Moscow State Textile University
Moskva, Moscow, Russia 
University of Pavia
Ticinum, Lombardy, Italy 
Università degli Studi di Genova
 Department of Physics
Genova, Liguria, Italy


1994–2010

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


1984–2009

INFN  Istituto Nazionale di Fisica Nucleare
Frascati, Latium, Italy


2008

Lomonosov Moscow State University
 Skobeltsyn Institute of Nuclear Physics
Moscow, Moscow, Russia


2003–2005

Sapienza University of Rome
 Department of Physics
Roma, Latium, Italy 
Universität Heidelberg
 Institute of Theoretical Physics
Heidelberg, BadenWuerttemberg, Germany


1990–1994

Università degli Studi di Perugia
 Department of Physics
Perugia, Umbria, Italy


1985

Istituto Superiore di Sanità
Roma, Latium, Italy
