We calculate the bag parameters for neutral B-meson mixing in and beyond the Standard Model, in full four-flavor lattice QCD for the first time. We work on gluon field configurations that include the ...effect of u, d, s, and c sea quarks with the highly improved staggered quark (HISQ) action at three values of the lattice spacing and with three u/d quark masses going down to the physical value. The valence b quarks use the improved nonrelativistic QCD action and the valence light quarks, the HISQ action. Our analysis was blinded. Our results for the bag parameters for all five operators are the most accurate to date. For the Standard Model operator between Bs and Bd mesons we find BBs = 1.232(53) and BBd = 1.222(61). Combining our results with lattice QCD calculations of the decay constants using HISQ quarks from the Fermilab/MILC Collaboration and with experimental values for Bs and Bd oscillation frequencies allows determination of the Cabibbo-Kobayashi-Maskawa (CKM) elements Vts and Vtd. We find |Vts| = 0.04189(93), |Vtd| = 0.00867(23), and |Vts|/|Vtd| = 0.2071(27). Our results agree well (within 2σ) with values determined from CKM unitarity constraints based on tree-level processes (only). Using a ratio to ΔMs,d in which CKM elements cancel in the Standard Model, we determine the branching fractions Br(Bs→μ+μ−) = 3.81(18)×10−9 and Br(Bd →μ+μ−)=1.031(54)×10−10. We also give results for matrix elements of the operators R0, R1, and R1 that contribute to neutral B-meson width differences.
FLAG Review 2021 Aoki, Y.; Blum, T.; Colangelo, G. ...
The European physical journal. C, Particles and fields,
10/2022, Letnik:
82, Številka:
10
Journal Article
Recenzirano
Odprti dostop
We review lattice results related to pion, kaon,
D
-meson,
B
-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More ...specifically, we report on the determination of the light-quark masses, the form factor
f
+
(
0
)
arising in the semileptonic
K
→
π
transition at zero momentum transfer, as well as the decay constant ratio
f
K
/
f
π
and its consequences for the CKM matrix elements
V
us
and
V
ud
. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of
S
U
(
2
)
L
×
S
U
(
2
)
R
and
S
U
(
3
)
L
×
S
U
(
3
)
R
Chiral Perturbation Theory. We review the determination of the
B
K
parameter of neutral kaon mixing as well as the additional four
B
parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for
m
c
and
m
b
as well as those for the decay constants, form factors, and mixing parameters of charmed and bottom mesons and baryons. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant
α
s
. We consider nucleon matrix elements, and review the determinations of the axial, scalar and tensor bilinears, both isovector and flavor diagonal. Finally, in this review we have added a new section reviewing determinations of scale-setting quantities.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We determine the normalization of scalar and pseudoscalar current operators made from nonrelativistic b quarks and highly improved staggered light quarks in lattice quantum chromodynamics (QCD) ...through O(αs) and ΛQCD/mb. We use matrix elements of these operators to extract B meson decay constants and form factors, and then compare to those obtained using the standard vector and axial-vector operators. This provides a test of systematic errors in the lattice QCD determination of the B meson decay constants and form factors. We provide a new value for the B and Bs meson decay constants from lattice QCD calculations on ensembles that include u, d, s, and c quarks in the sea and those that have the u/d quark mass going down to its physical value. Our results are fB=0.196(6) GeV, fBs=0.236(7) GeV, and fBs/fB=1.207(7), agreeing well with earlier results using the temporal axial current. By combining with these previous results, we provide updated values of fB=0.190(4) GeV, fBs=0.229(5) GeV, and fBs/fB=1.206(5).
The axial coupling of the nucleon, g
, is the strength of its coupling to the weak axial current of the standard model of particle physics, in much the same way as the electric charge is the strength ...of the coupling to the electromagnetic current. This axial coupling dictates the rate at which neutrons decay to protons, the strength of the attractive long-range force between nucleons and other features of nuclear physics. Precision tests of the standard model in nuclear environments require a quantitative understanding of nuclear physics that is rooted in quantum chromodynamics, a pillar of the standard model. The importance of g
makes it a benchmark quantity to determine theoretically-a difficult task because quantum chromodynamics is non-perturbative, precluding known analytical methods. Lattice quantum chromodynamics provides a rigorous, non-perturbative definition of quantum chromodynamics that can be implemented numerically. It has been estimated that a precision of two per cent would be possible by 2020 if two challenges are overcome
: contamination of g
from excited states must be controlled in the calculations and statistical precision must be improved markedly
. Here we use an unconventional method
inspired by the Feynman-Hellmann theorem that overcomes these challenges. We calculate a g
value of 1.271 ± 0.013, which has a precision of about one per cent.
In the psychological tradition, desistance from antisocial behavior is viewed as the product of psychosocial maturation, including increases in the ability to control impulses, consider the ...implications of one's actions on others, delay gratification in the service of longer term goals, and resist the influences of peers. The present study investigates how individual variability in the development of psychosocial maturity is associated with desistance from antisocial behavior in a sample of 1,088 serious juvenile offenders followed from adolescence to early adulthood (ages 14-25). We find that psychosocial maturity continues to develop to the midtwenties and that different developmental patterns of maturation are found among those who desist and those who persist in antisocial behavior. Compared to individuals who desisted from antisocial behavior, youths who persisted exhibited diminished development of psychosocial maturity. Moreover, earlier desistance compared to later desistance is linked to greater psychosocial maturity, suggesting that there is an association between desistance from antisocial behavior and normative increases in psychosocial maturity.
We present the first lattice QCD calculation of the decay constants f(B) and f(B(s)) with physical light quark masses. We use configurations generated by the MILC Collaboration including the effect ...of u, d, s, and c highly improved staggered quarks in the sea at three lattice spacings and with three u/d quark mass values going down to the physical value. We use improved nonrelativistic QCD (NRQCD) for the valence b quarks. Our results are f(B)=0.186(4) GeV, f(B(s))=0.224(4) GeV, f(B(s))/f(B)=1.205(7), and M(B(s))-M(B)=85(2) MeV, superseding earlier results with NRQCD b quarks. We discuss the implications of our results for the standard model rates for B((s))→μ(+)μ(-) and B→τν.
A new sea spray source function (SSSF), termed Oceanflux Sea Spray Aerosol or OSSA, was derived based on in-situ sea spray aerosol measurements along with meteorological/physical parameters. ...Submicron sea spray aerosol fluxes derived from particle number concentration measurements at the Mace Head coastal station, on the west coast of Ireland, were used together with open-ocean eddy correlation flux measurements from the Eastern Atlantic Sea Spray, Gas Flux, and Whitecap (SEASAW) project cruise. In the overlapping size range, the data for Mace Head and SEASAW were found to be in a good agreement, which allowed deriving the new SSSF from the combined dataset spanning the dry diameter range from 15 nm to 6 μm. The OSSA source function has been parameterized in terms of five lognormal modes and the Reynolds number instead of the more commonly used wind speed, thereby encapsulating important influences of wave height, wind history, friction velocity, and viscosity. This formulation accounts for the different flux relationships associated with rising and waning wind speeds since these are included in the Reynolds number. Furthermore, the Reynolds number incorporates the kinematic viscosity of water, thus the SSSF inherently includes dependences on sea surface temperature and salinity. The temperature dependence of the resulting SSSF is similar to that of other in-situ derived source functions and results in lower production fluxes for cold waters and enhanced fluxes from warm waters as compared with SSSF formulations that do not include temperature effects.
The current study compares 3 distinct approaches for measuring juvenile psychopathy and their utility for predicting short- and long-term recidivism among a sample of 1,170 serious male juvenile ...offenders. The assessment approaches compared a clinical interview method (the Psychopathy Checklist: Youth Version PCL:YV;
Forth, Kosson, & Hare, 2003
), a new self-report measure (the Youth Psychopathic Traits Inventory;
Andershed, Kerr, Stattin, & Levander, 2002
), and a personality-based approach (the NEO Psychopathy Resemblance Index;
Lynam & Widiger, 2007
). Results indicate a modest overlap between the 3 measures (
r
s = .26-.36); however, youths were often identified as psychopathic by 1 measure but not by others. Measures were weakly correlated with reoffending during subsequent 6- and 12-month periods. Findings suggest that although such scores may be useful indicators of the need for heightened monitoring in the short term, care should be taken when making predictions about long-term recidivism among adolescents. Moreover, the lack of long-term predictive power for the PCL:YV and the inconsistent psychopathy designations obtained with different measures raise serious questions about the use of such measures as the basis for legal or clinical treatment decisions.
Prior research describes the development of susceptibility to peer pressure in adolescence as following an inverted U-shaped curve, increasing during early adolescence, peaking around age 14, and ...declining thereafter. This pattern, however, is derived mainly from studies that specifically examined peer pressure to engage in antisocial behavior. In the present study, age differences and developmental change in resistance to peer influence were assessed using a new self-report instrument that separates susceptibility to peer pressure from willingness to engage in antisocial activity. Data from four ethnically and socioeconomically diverse samples comprising more than 3,600 males and females between the ages of 10 and 30 were pooled from one longitudinal and two cross-sectional studies. Results show that across all demographic groups, resistance to peer influences increases linearly between ages 14 and 18. In contrast, there is little evidence for growth in this capacity between ages 10 and 14 or between 18 and 30. Middle adolescence is an especially significant period for the development of the capacity to stand up for what one believes and resist the pressures of one's peers to do otherwise.
PDF
