65 research outputs found
EWPD Constraints on Flavor Symmetric Vector Fields
Electroweak precision data constraints on flavor symmetric vector fields are
determined. The flavor multiplets of spin one that we examine are the complete
set of fields that couple to quark bi-linears at tree level while not initially
breaking the quark global flavor symmetry group. Flavor safe vector masses
proximate to, and in some cases below, the electroweak symmetry breaking scale
are found to be allowed. Many of these fields provide a flavor safe mechanism
to explain the t tbar forward backward anomaly, and can simultaneously
significantly raise the allowed values of the Standard Model Higgs mass
consistent with electroweak precision data.Comment: Matches version published in JHE
Dark Matter from Minimal Flavor Violation
We consider theories of flavored dark matter, in which the dark matter
particle is part of a multiplet transforming nontrivially under the flavor
group of the Standard Model in a manner consistent with the principle of
Minimal Flavor Violation (MFV). MFV automatically leads to the stability of the
lightest state for a large number of flavor multiplets. If neutral, this
particle is an excellent dark matter candidate. Furthermore, MFV implies
specific patterns of mass splittings among the flavors of dark matter and
governs the structure of the couplings between dark matter and ordinary
particles, leading to a rich and predictive cosmology and phenomenology. We
present an illustrative phenomenological study of an effective theory of a
flavor SU(3)_Q triplet, gauge singlet scalar.Comment: 10 pages, 2 figures; v2: references added, minor changes to collider
analysis, conclusions unchange
Electroweak Baryogenesis in Two Higgs Doublet Models and B meson anomalies
Motivated by 3.9 sigma evidence of a CP-violating phase beyond the standard
model in the like-sign dimuon asymmetry reported by DO, we examine the
potential for two Higgs doublet models (2HDMs) to achieve successful
electroweak baryogenesis (EWBG) while explaining the dimuon anomaly. Our
emphasis is on the minimal flavour violating 2HDM, but our numerical scans of
model parameter space include type I and type II models as special cases. We
incorporate relevant particle physics constraints, including electroweak
precision data, b to s gamma, the neutron electric dipole moment, R_b, and
perturbative coupling bounds to constrain the model. Surprisingly, we find that
a large enough baryon asymmetry is only consistently achieved in a small subset
of parameter space in 2HDMs, regardless of trying to simultaneously account for
any B physics anomaly. There is some tension between simultaneous explanation
of the dimuon anomaly and baryogenesis, but using a Markov chain Monte Carlo we
find several models within 1 sigma of the central values. We point out
shortcomings with previous studies that reached different conclusions. The
restricted parameter space that allows for EWBG makes this scenario highly
predictive for collider searches. We discuss the most promising signatures to
pursue at the LHC for EWBG-compatible models.Comment: 58 pages, 16 figures, 6 tables; v2 added references; v3 minor
corrections and improvements, published versio
Renormalization group evolution of the Standard Model dimension six operators II: Yukawa dependence
Differential branching fraction and angular analysis of the decay B0s→ ϕμ+μ−
The determination of the differential branching fraction and the first angular analysis of the decay B[superscript 0][subscript 0] → ϕμ[superscript +]μ[subscript −] are presented using data, corresponding to an integrated luminosity of 1.0 fb[superscript −1], collected by the LHCb experiment at s√=7s=7 TeV. The differential branching fraction is determined in bins of q[superscript 2], the invariant dimuon mass squared. Integration over the full q[superscript 2] range yields a total branching fraction of B(B[superscript 0][subscript s]→ϕμ[superscript +]μ[subscript −])=(7.07[superscript +0.64][subscript −0.59]±0.71±0.71)) × 10[subscript −7], where the first uncertainty is statistical, the second systematic, and the third originates from the branching fraction of the normalisation channel. An angular analysis is performed to determine the angular observables F[subscript L], S[subscript 3], A[subscript 6], and A[subscript 9]. The observables are consistent with Standard Model expectations.National Science Foundation (U.S.
Updated Determination of D⁰–D¯⁰Mixing and CP Violation Parameters with D⁰→K⁺π⁻ Decays
We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of D⁰→K⁺π⁻ to D⁰→K⁻π⁺ rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of 5.0 fb⁻¹ recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters are determined to be x′²=(3.9±2.7)×10⁻⁵, y′=(5.28±0.52)×10⁻³, and R[subscript D]=(3.454±0.031)×10⁻³. Without this assumption, the measurement is performed separately for D⁰ and D[over ¯]⁰ mesons, yielding a direct CP-violating asymmetry A[subscript D]=(-0.1±9.1)×10⁻³, and magnitude of the ratio of mixing parameters 1.00<|q/p|<1.35 at the 68.3% confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed
Observation of D⁰ Meson Decays to Π⁺π⁻μ⁺μ⁻ and K⁺K⁻μ⁺μ⁻ Final States
The first observation of the D⁰→π⁺π⁻μ⁺μ⁻ and D⁰→K⁺K⁻μ⁺μ⁻ decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass energy of 8 TeV, and corresponding to 2 fb⁻¹ of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay D⁰→K⁻π⁺[μ⁺μ⁻][subscript ρ⁰/ω], where the two muons are consistent with coming from the decay of a ρ⁰ or ω meson. The results are B(D⁰→π⁺π⁻μ⁺μ⁻)=(9.64±0.48±0.51±0.97)×10⁻⁷ and B(D⁰→K⁺K⁻μ⁺μ⁻)=(1.54±0.27±0.09±0.16)×10⁻⁷, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated
NSUSY fits
We perform a global fit to Higgs signal-strength data in the context of light
stops in Natural SUSY. In this case, the Wilson coefficients of the higher
dimensional operators mediating g g -> h and h -> \gamma \gamma, given by c_g,
c_\gamma, are related by c_g = 3 (1 + 3 \alpha_s/(2 \pi)) c_\gamma/8. We
examine this predictive scenario in detail, combining Higgs signal-strength
constraints with recent precision measurements of m_W, b-> s \gamma constraints
and direct collider bounds on weak scale SUSY, finding regions of parameter
space that are consistent with all of these constraints. However it is
challenging for the allowed parameter space to reproduce the observed Higgs
mass value with sub-TeV stops. We discuss some of the direct stop discovery
prospects and show how global Higgs fits can be used to exclude light stop
parameter space difficult to probe by direct collider searches. We determine
the current status of such indirect exclusions and estimate their reach by the
end of the 8 TeV LHC run.Comment: 41 pages, 13 figures. v3: final JHEP version, b to s gamma updated to
latest data and typos correcte
Updated determination of D 0 - D 0 mixing and C P violation parameters with D 0 → K + π -
We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of D0→K+π- to D0→K-π+ rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of 5.0 fb-1 recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters are determined to be x′2=(3.9±2.7)×10-5, y′=(5.28±0.52)×10-3, and RD=(3.454±0.031)×10-3. Without this assumption, the measurement is performed separately for D0 and D0 mesons, yielding a direct CP-violating asymmetry AD=(-0.1±9.1)×10-3, and magnitude of the ratio of mixing parameters 1.00<|q/p|<1.35 at the 68.3% confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed
The Physics of the B Factories
This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C
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