4,103 research outputs found
The estimation of neutrino fluxes produced by proton-proton collisions at TeV of the LHC
Intense and collimated neutrino beams are produced by charm and beauty
particle decays from proton-proton collisions at the LHC. A neutrino experiment
would be run parasitically without interrupting the LHC physics program during
the collider run. We estimate the neutrino fluxes from proton-proton collisions
at TeV of the LHC with the designed luminosity, 10^{34} \lumi.
By mounting about 200 tons of fiducial volume of a neutrino detector at 300
\m away from the interaction point, about 150,000 of charged current neutrino
events per year can be observable.Comment: 8 pages, Accepted in JHE
Cornering New Physics in b --> s Transitions
We derive constraints on Wilson coefficients of dimension-six effective
operators probing the b --> s transition, using recent improved measurements of
the rare decays Bs --> mu+mu-, B --> K mu+mu- and B --> K* mu+mu- and including
all relevant observables in inclusive and exclusive decays. We consider
operators present in the SM as well as their chirality-flipped counterparts and
scalar operators. We find good agreement with the SM expectations. Compared to
the situation before winter 2012, we find significantly more stringent
constraints on the chirality-flipped coefficients due to complementary
constraints from B --> K mu+mu- and B --> K* mu+mu- and due to the LHCb
measurement of the angular observable S_3 in the latter decay. We also list the
full set of observables sensitive to new physics in the low recoil region of B
--> K* mu+mu-.Comment: 18 pages, 6 figures, 4 tables. v3: typos correcte
Supersymmetric constraints from Bs -> mu+mu- and B -> K* mu+mu- observables
We study the implications of the recent LHCb limit and results on Bs ->
mu+mu- and B -> K* mu+mu- observables in the constrained SUSY scenarios. After
discussing the Standard Model predictions and carefully estimating the
theoretical errors, we show the constraining power of these observables in
CMSSM and NUHM. The latest limit on BR(Bs -> mu+mu-), being very close to the
SM prediction, constrains strongly the large tan(beta) regime and we show that
the various angular observables from B -> K* mu+mu- decay can provide
complementary information in particular for moderate tan(beta) values.Comment: 30 pages, 14 figure
Bayesian Fit of Exclusive Decays: The Standard Model Operator Basis
We perform a model-independent fit of the short-distance couplings
within the Standard Model set of and operators. Our analysis of , and decays is the first to harness the full
power of the Bayesian approach: all major sources of theory uncertainty
explicitly enter as nuisance parameters. Exploiting the latest measurements,
the fit reveals a flipped-sign solution in addition to a Standard-Model-like
solution for the couplings . Each solution contains about half of the
posterior probability, and both have nearly equal goodness of fit. The Standard
Model prediction is close to the best-fit point. No New Physics contributions
are necessary to describe the current data. Benefitting from the improved
posterior knowledge of the nuisance parameters, we predict ranges for currently
unmeasured, optimized observables in the angular distributions of .Comment: 42 pages, 8 figures; v2: Using new lattice input for f_Bs,
considering Bs-mixing effects in BR[B_s->ll]. Main results and conclusion
unchanged, matches journal versio
Universal Constraints on Low-Energy Flavour Models
It is pointed out that in a general class of flavour models one can identify
certain universally present FCNC operators, induced by the exchange of heavy
flavour messengers. Their coefficients depend on the rotation angles that
connect flavour and fermion mass basis. The lower bounds on the messenger scale
are derived using updated experimental constraints on the FCNC operators. The
obtained bounds are different for different operators and in addition they
depend on the chosen set of rotations. Given the sensitivity expected in the
forthcoming experiments, the present analysis suggests interesting room for
discovering new physics. As the highlights emerge the leptonic processes,
, and
conversion in nuclei.Comment: 18 pages, 3 figures; v2 matches published versio
Implications from clean observables for the binned analysis of B -> K*ll at large recoil
We perform a frequentist analysis of q^2-dependent B-> K*(->Kpi)ll angular
observables at large recoil, aiming at bridging the gap between current
theoretical analyses and the actual experimental measurements. We focus on the
most appropriate set of observables to measure and on the role of the
q^2-binning. We highlight the importance of the observables P_i exhibiting a
limited sensitivity to soft form factors for the search for New Physics
contributions. We compute predictions for these binned observables in the
Standard Model, and we compare them with their experimental determination
extracted from recent LHCb data. Analyzing b->s and b->sll transitions within
four different New Physics scenarios, we identify several New Physics benchmark
points which can be discriminated through the measurement of P_i observables
with a fine q^2-binning. We emphasise the importance (and risks) of using
observables with (un)suppressed dependence on soft form factors for the search
of New Physics, which we illustrate by the different size of hadronic
uncertainties attached to two related observables (P_1 and S_3). We illustrate
how the q^2-dependent angular observables measured in several bins can help to
unravel New Physics contributions to B-> K*(->Kpi)ll, and show the
extraordinary constraining power that the clean observables will have in the
near future. We provide semi-numerical expressions for these observables as
functions of the relevant Wilson coefficients at the low scale.Comment: 50 pages, 21 figures. Improved form factor analysis, conclusions
unchanged. Plots with full resolution. Version published in JHE
Less Minimal Flavour Violation
We consider the approximate U(2)^3 flavour symmetry exhibited by the quark
sector of the Standard Model and all its possible breaking terms appearing in
the quark Yukawa couplings. Taking an Effective Field Theory point of view, we
determine the current bounds on these parameters, assumed to control the
breaking of flavour in a generic extension of the Standard Model at a reference
scale Lambda. In particular, a significant bound from epsilon'/epsilon is
derived, which is relevant to Minimal Flavour Violation as well. In the
up-quark sector, the recently observed CP violation in D -> pi+ pi-, K+ K-
decays might be accounted for in this generic framework, consistently with any
other constraint.Comment: 15 pages, 1 figur
The UTfit Collaboration Average of D meson mixing data: Spring 2012
We derive constraints on the parameters , and
that describe meson mixing using all available data, allowing
for CP violation. We also provide posterior distributions and predictions for
observable parameters appearing in physics.Comment: 5 pages, 3 figure
The small x gluon and b\bar{b} production at the LHC
We study open b\bar{b} production at large rapidity at the LHC in an attempt
to pin down the gluon distribution at very low x. For the LHC energy of 7 TeV,
at next-to-leading order (NLO), there is a large factorization scale
uncertainty. We show that the uncertainty can be greatly reduced if events are
selected in which the transverse momenta of the two B-mesons balance each other
to some accuracy, that is |\vec p_{1T}+\vec p_{2T}| < k_0. This will fix the
scale \mu_F \simeq k_0, and will allow the LHCb experiment, in particular, to
study the x-behaviour of gluon distribution down to x ~ 10^{-5}, at rather low
scales, \mu ~ 2 GeV. We evaluate the expected cross sections using, for
illustrative purposes, various recent sets of Parton Distribution Functions.Comment: 13 pages, 5 figure
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