We perform a manifestly gauge-independent analysis of the vacuum stability in the standard model including two-loop matching, three-loop renormalization group evolution, and pure QCD corrections ...through four loops. All these ingredients are exact, except that light-fermion masses are neglected. We in turn apply the criterion of nullifying the Higgs self-coupling and its beta function in the modified minimal-subtraction scheme and a recently proposed consistent method for determining the true minimum of the effective Higgs potential that also avoids gauge dependence. Exploiting our knowledge of the Higgs-boson mass, we derive an upper bound on the pole mass of the top quark by requiring that the standard model be stable all the way up to the Planck mass scale and conservatively estimate the theoretical uncertainty. This bound is compatible with the Monte Carlo mass quoted by the Particle Data Group at the 1.3σ level.
We study inclusive
B
-meson production in
pp
collisions at the LHC and compare experimental data with predictions of the general-mass variable-flavour-number scheme at next-to-leading order of ...perturbative QCD. We find almost perfect agreement provided that the factorization scale parameters and the parton distribution functions are chosen appropriately.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
We argue that the renormalization factors for non-local quark-antiquark and gluon operators at space-like and time-like separations connected by a Wilson line coincide to all orders in ...perturbation theory. We calculate the anomalous dimensions and renormalization constants of quark-antiquark and gluon operators to three- and two-loop accuracy, respectively, and also compute vacuum expectation values of these operators to three-loop accuracy.
We compute the nonplanar contribution to the universal anomalous dimension of the SU(4)-singlet twist-two operators in N=4 supersymmetric Yang-Mills theory at four loops through Lorentz spin 18. From ...this, we numerically evaluate the nonplanar contribution to the four-loop lightlike cusp anomalous dimension and derive the transcendental ζ_{3} and ζ_{5} parts of the universal anomalous dimension for arbitrary Lorentz spin in analytic form. As for the lightlike cusp anomalous dimension and the ζ_{5} part of the universal anomalous dimension, we confirm previous results.
A
bstract
We present predictions for the prompt-neutrino flux arising from the decay of charmed mesons and baryons produced by the interactions of high-energy cosmic rays in the Earth’s atmosphere, ...making use of a QCD approach on the basis of the general-mass variable-flavor-number scheme for the description of charm hadroproduction at NLO, complemented by a consistent set of fragmentation functions. We compare the theoretical results to those already obtained by our and other groups with different theoretical approaches. We provide comparisons with the experimental results obtained by the IceCube Collaboration in two different analyses and we discuss the implications for parton distribution functions.
A
bstract
We evaluate the three-loop massive vacuum bubble diagrams in terms of polylogarithms up to weight six. We also construct the basis of irrational constants being harmonic polylgarithms of ...arguments
e
kiπ
/3
.
We perform direct diagrammatic calculations of the anomalous dimensions of twist-two operators in extended N=2 and N=4 super Yang-Mills theories (SYM). In the case of N=4 SYM, we compute the ...four-loop anomalous dimension of the twist-two operator for several fixed values of Lorentz spin. This is the first direct diagrammatic calculation of this kind, and we confirm results previously obtained by means of integrability. For N=2 SYM, we obtain the general result for the anomalous dimension at third order of perturbation theory and find the three-loop Cusp anomalous dimension.
We compute the non-planar contribution to the universal anomalous dimension of twist-two operators in N=4 supersymmetric Yang-Mills theory at four loops through Lorentz spin eighteen. Exploiting the ...results of this and our previous calculations along with recent analytic results for the cusp anomalous dimension and some expected analytic properties, we reconstruct a general expression valid for arbitrary Lorentz spin. We study various properties of this general result, such as its large-spin limit, its small-x limit, and others. In particular, we present a prediction for the non-planar contribution to the anomalous dimension of the single-magnon operator in the β-deformed version of the theory.
Inclusive charmed-meson production at the CERN LHC Kniehl, Bernd A.; Kramer, Gustav; Schienbein, Ingo ...
The European physical journal. C, Particles and fields,
07/2012, Letnik:
72, Številka:
7
Journal Article
Recenzirano
Odprti dostop
We present predictions for the inclusive production of
D
mesons at the CERN LHC in the general-mass variable-flavor-number scheme at next-to-leading order. Detailed numerical results are compared to ...data where available, or presented in a way to ease future comparisons with experimental results. We also point out that measurements at large rapidity have the potential to pin down models of intrinsic charm.
We perform a number of improvements to the previous AKK extraction of fragmentation functions for
π
±
,
K
±
,
p
/
p
¯
,
K
S
0
and
Λ
/
Λ
¯
particles at next-to-leading order. Inclusive hadron ...production measurements from
p
p
(
p
¯
)
reactions at BRAHMS, CDF, PHENIX and STAR are added to the data sample. We use the charge-sign asymmetry of the produced hadrons in
pp reactions to constrain the valence quark fragmentations. Data from
e
+
e
−
reactions in regions of smaller
x and lower
s
are added. Hadron mass effects are treated for all observables and, for each particle, the hadron mass used for the description of the
e
+
e
−
reaction is fitted. The baryons' fitted masses are found to be only around 1% above their true masses, while the values of the mesons' fitted masses have the correct order of magnitude. Large
x resummation is applied in the coefficient functions of the
e
+
e
−
reactions, and also in the evolution of the fragmentation functions, which in most cases results in a significant reduction of the minimized
χ
2
. To further exploit the data, all published normalization errors are incorporated via a correlation matrix.
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