128 research outputs found
Baryon Number, Lepton Number, and Operator Dimension in the Standard Model
We prove that for a given operator in the Standard Model (SM) with baryon
number B and lepton number L, that the operator's dimension is even (odd) if
(B-L)/2 is even (odd). Consequently, this establishes the veracity of
statements that were long observed or expected to be true, but not proven,
e.g., operators with B-L=0 are of even dimension, B-L must be an even number,
etc. These results remain true even if the SM is augmented by any number of
right-handed neutrinos with L=1.Comment: 5 page
Gravitational Effects on Measurements of the Muon Dipole Moments
If the technology for muon storage rings one day permits sensitivity to
precession at the order of Hz, the local gravitational field of Earth
can be a dominant contribution to the precession of the muon, which, if
ignored, can fake the signal for a nonzero muon electric dipole moment (EDM).
Specifically, the effects of Earth's gravity on the motion of a muon's spin is
indistinguishable from it having a nonzero EDM of magnitude e cm in a storage ring with vertical magnetic field of 1 T,
which is significantly larger than the expected upper limit in the Standard
Model, e cm. As a corollary, measurements of Earth's
local gravitational field using stored muons would be a unique test to
distinguish classical gravity from general relativity with a bonafide quantum
mechanical entity, i.e., an elementary particle's spin.Comment: 5 pages; corrected calculation, qualitative results unchange
Hilbert Series and Operator Basis for NRQED and NRQCD/HQET
We use a Hilbert series to construct an operator basis in the expansion
of a theory with a nonrelativistic heavy fermion in an electromagnetic (NRQED)
or color gauge field (NRQCD/HQET). We present a list of effective operators
with mass dimension . Comparing to the current literature, our results
for NRQED agree for , but there are some discrepancies in NRQCD/HQET
at and 8.Comment: 13 pages, 1 figure, 3 tables. Minor typographical errors correcte
Model-Independent Extraction of from
We fit the unfolded data of
from the Belle experiment, where , using a method
independent of heavy quark symmetry to extrapolate to zero-recoil and extract
the value of . This results in , which is robust to changes in the
theoretical inputs and very consistent with the value extracted from inclusive
semileptonic decays.Comment: 8 pages, 3 figures; corrected minor typographical error
Lepton-Flavored Dark Matter
In this work, we address two paradoxes. The first is that the measured
dark-matter relic density can be satisfied with new physics at O(100 GeV - 1
TeV), while the null results from direct-detection experiments place lower
bounds of O(10 TeV) on a new-physics scale. The second puzzle is that the
severe suppression of lepton-flavor-violating processes involving electrons,
e.g. mu->3e, tau->e mu mu, etc., implies that generic new-physics contributions
to lepton interactions cannot exist below O(10 - 100 TeV), whereas the 3.6sigma
deviation of the muon g-2 from the standard model can be explained by a
new-physics scale < O(1 TeV). Here, we suggest that it may not be a coincidence
that both the muon g-2 and the relic density can be satisfied by a new-physics
scale < 1 TeV. We consider the possibility of a gauged lepton-flavor
interaction that couples at tree level only to mu- and tau-flavored leptons and
the dark sector. Dark matter thus interacts appreciably only with particles of
mu and tau flavor at tree level and has loop-suppressed couplings to quarks and
electrons. Remarkably, if such a gauged flavor interaction exists at a scale
O(100 GeV - 1 TeV), it allows for a consistent phenomenological framework,
compatible with the muon g-2, the relic density, direct detection, indirect
detection, charged-lepton decays, neutrino trident production, and results from
hadron and e+e- colliders. We suggest experimental tests for these ideas at
colliders and for low-energy observables.Comment: includes additional discussions, results unchange
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