Search results for "Strange"
showing 10 items of 551 documents
Geometrical volume effects in the computation of the slope of the isgur-wise function
1994
We use a method recently suggested for evaluating the slope of the Isgur-Wise function, at the zero-recoil point, on the lattice. The computations are performed in the quenched approximation to lattice QCD, on a $24^3 \times 48$ lattice at $\beta=6.2$, using an $O(a)$-improved action for the fermions. We have found unexpectedly large finite-volume effects in such a calculation. These volume corrections turned out to be purely geometrical and independent of the dynamics of the system. After the study of these effects on a smaller volume and for different quark masses, we give approximate expressions that account for them. Using these approximations we find $\xi^\prime(1)=-1.7 \pm 0.2$ and $\…
Flavour symmetry restoration and kaon weak matrix elements in quenched twisted mass QCD
2007
We simulate two variants of quenched twisted mass QCD (tmQCD), with degenerate Wilson quarks of masses equal to or heavier than half the strange quark mass. We use Ward identities in order to measure the twist angles of the theory and thus check the quality of the tuning of mass parameters to a physics condition which stays constant as the lattice spacing is varied. Flavour symmetry breaking in tmQCD is studied in a framework of two fully twisted and two standard Wilson quark flavours, tuned to be degenerate in the continuum. Comparing pseudoscalar masses, obtained from connected quark diagrams made of tmQCD and/or standard Wilson quark propagators, we confirm that flavour symmetry breaking…
Up, down, strange and charm quark masses withNf=2+1+1twisted mass lattice QCD
2014
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 N f = 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 …
Strange quark mass from the invariant mass distribution of Cabibbo-suppressed tau decays
2001
8 páginas, 4 figuras, 4 tablas.-- arXiv:hep-ph/0105253v1
CLS 2+1 flavor simulations at physical light-and strange-quark masses
2017
We report recent efforts by CLS to generate an ensemble with physical light- and strange-quark masses in a lattice volume of 192x96^3 at $\beta=3.55$ corresponding to a lattice spacing of 0.064 fm. This ensemble is being generated as part of the CLS 2+1 flavor effort with improved Wilson fermions. Our simulations currently cover 5 lattice spacings ranging from 0.039 fm to 0.086 fm at various pion masses along chiral trajectories with either the sum of the quark masses kept fixed, or with the strange-quark mass at the physical value. The current status of simulations is briefly reviewed, including a short discussion of measured autocorrelation times and of the main features of the simulation…
Consistency between SU(3) and SU(2) covariant baryon chiral perturbation theory for the nucleon mass
2017
Abstract Treating the strange quark mass as a heavy scale compared to the light quark mass, we perform a matching of the nucleon mass in the SU(3) sector to the two-flavor case in covariant baryon chiral perturbation theory. The validity of the 19 low-energy constants appearing in the octet baryon masses up to next-to-next-to-next-to-leading order [1] is supported by comparing the effective parameters (the combinations of the 19 couplings) with the corresponding low-energy constants in the SU(2) sector [2] . In addition, it is shown that the dependence of the effective parameters and the pion-nucleon sigma term on the strange quark mass is relatively weak around its physical value, thus pro…
Probing the chiral regime of Nf=2 QCD with mixed actions
2011
17 páginas, 15 figuras, 9 tablas.-- El Pdf es la versión pre-print del artículo: arXiv:1008.1870v2
Strange quark parton distribution functions and implications for Drell-Yan boson production at the LHC
2012
Global analyses of parton distribution functions (PDFs) have provided incisive constraints on the up and down quark components of the proton, but constraining the other flavor degrees of freedom is more challenging. Higher-order theory predictions and new data sets have contributed to recent improvements. Despite these efforts, the strange quark parton distribution function has a sizable uncertainty, particularly in the small $x$ region. We examine the constraints from experiment and theory, and investigate the impact of this uncertainty on LHC observables. In particular, we study $W/Z$ production to see how the $s$ quark uncertainty propagates to these observables, and examine the extent t…
Rapidity distributions of dileptons from a hadronizing quark-gluon plasma
1994
It has been predicted that dilepton production may be used as a quark-gluon plasma probe. We calculate the rapidity distributions of thermal dileptons produced by an evolving quark-gluon plasma assuming a longitudinal scaling expansion with initial conditions locally determined from the hadronic rapidity density. These distributions are compared with Drell-Yan production and semileptonic charm decays at invariant mass $M = 2$, 4, and 6 GeV.
Shock phenomena in baryonless strongly interacting matter.
1987
Shock phenomena associated with the quark-to-hadron matter phase transition are studied using the concept of adiabats. To allow for an analysis of a medium with vanishing baryon density, the shock and Poisson adiabats are formulated in terms of hydrodynamic fluxes, rather than only thermodynamic variables. The bag-model equation of state is used to describe the phase transition. It is shown that deflagrations from the quark phase above the critical temperature and strong detonations from the supercooled quark phase to the superheated hadron phase are unlikely. Instead the possibility of weak condensation detonations from the supercooled quark phase to a mixed phase is indicated. Strong deto…