We analyze the interevent time distribution of hydraulic‐fracturing‐induced seismicity collected during 18 stages at four different regions. We identify a universal statistical process describing the ...distribution of hydraulic‐fracturing‐induced events in time. The distribution of waiting times between subsequently occurring events is given by the exponential probability density function of the homogeneous Poisson process. Our findings suggest that hydraulic‐fracturing‐induced seismicity is directly triggered by the relaxation of stress and pore pressure perturbation initially created by the injection. Therefore, compared to this relaxation, the stress transfer caused by the occurrence of preceding seismic events is mainly insignificant for the seismogenesis of subsequently occurring events. We develop a statistical model to compute the occurrence probability of hydraulic‐fracturing‐induced seismicity. This model can be used to assess the seismic hazard associated with hydraulic fracturing operations. No aftershock triggering has to be included in the statistical model.
Key Points
Statistical model to compute the occurrence probability of hydraulic‐fracturing‐induced seismicity
Seismicity is triggered by relaxation of stress and pore pressure perturbation by injection
No aftershocks have to be included in statistical models of hydro‐fracturing induced seismicity
A method to directly determine the Wilson coefficients for rare b → s transitions using B$^{0}$ → K$^{∗0}$ μ$^{+}$ μ$^{−}$ decays in an unbinned maximum likelihood fit is presented. The method has ...several advantages compared to the conventional determination of the Wilson coefficients from angular observables that are determined in bins of q$^{2}$, the square of the mass of the dimuon system. The method uses all experimental information in a more efficient way and automatically accounts for experimental correlations. Performing pseudoexperiments, we show the improved sensitivity of the proposed method for the Wilson coefficients. We also demonstrate that it will be possible to use the method with the combined Run 1 and 2 data sample taken by the LHCb experiment.
We analyze the inter event time distribution of fluid‐injection‐induced earthquakes for six catalogs collected at geothermal injection sites at Soultz‐sous‐Forêts and Basel. We find that the ...distribution of waiting times during phases of constant seismicity rate coincides with the exponential distribution of the homogeneous Poisson process (HPP). We analyze the waiting times for the complete event catalogs and find that, as for naturally occurring earthquakes, injection induced earthquakes are distributed according to a non homogeneous Poisson process in time. Moreover, the process of event occurrence in the injection volume domain is a HPP. These results indicate that fluid‐injection‐induced earthquakes are directly triggered by the loading induced by the fluid injection. We also consider the spatial distance between events and perform a nearest neighbor analysis in the time‐space‐magnitude domain. Our analysis including a comparison to a synthetic catalog created according to the ETAS model reveals no signs of causal relationships between events. Therefore, coupling effects between events are very weak. The Poisson model seems to be a very good approximation of fluid induced seismicity.
Key Points
The inter event times of fluid induced earthquakes are exponentially distributed
The Poisson model can be applied to calculate occurrence probabilities of events
Aftershock triggering seems to be negligible for fluid induced earthquakes
Flavour anomalies in heavy quark decays Albrecht, J.; van Dyk, D.; Langenbruch, C.
Progress in particle and nuclear physics,
September 2021, 2021-09-00, Letnik:
120
Journal Article
Recenzirano
Odprti dostop
Recent measurements of b-hadron decays show a pattern of consistent tensions with the respective Standard Model (SM) predictions. These tensions appear both in the sector of rare flavour-changing ...neutral currents and in tree-level semileptonic b-hadron decays. Flavour-changing neutral-current decays are loop-suppressed in the SM and are thus very susceptible to contributions from new heavy particles and/or new interactions beyond the SM.
In rare semileptonic decays tensions are observed in measurements of branching fractions and angular observables, as well as in lepton flavour universality tests. Lepton flavour universality is also tested by comparing tree-level b→cℓ−ν̄τ processes involving third generation leptons ℓ=τ to semileptonic decays with light leptons ℓ=e,μ in the final state. These tests also show tensions between measurements and the SM prediction.
Taken together, these tensions constitute the so-called flavour anomalies in b-hadron decays, and could be first signs of New Physics (NP) beyond the SM, if established beyond any reasonable doubt. This article reviews both the current experimental status of the flavour anomalies and developments for the relevant theoretical predictions. The review concludes with a discussion of future prospects for the field.
Based on measurements along boreholes, a characterization of the Earth's crust elastic heterogeneity is presented. We investigate its impact on Coulomb stress distribution and earthquake magnitude ...scaling. The analysis of elastic modulus distribution at various borehole locations in different regions reveals universal fractal nature of elastic heterogeneity. By applying a homogeneous far‐field stress to a representative model of elastic rock heterogeneity, we show that it causes strong Coulomb stress fluctuations. In situ fluctuations of Coulomb stress are mainly controlled by in situ elastic moduli. Fluctuations caused by surrounding heterogeneities are only of minor importance. Hence, the fractal nature of elastic heterogeneity results in Coulomb stress fluctuations with power law size distribution. As a consequence, fault sizes and magnitudes of earthquakes scale according to the Gutenberg‐Richter relation. Due to the universal fractal nature of elastic heterogeneity, the b value should be universal. Deviation from its universal value of b≈1 occurs due to characteristic scales of seismogenic processes, which cause limitations or changes of fractal scaling. Scale limitations are also the reason for observed stress dependency of the b value. Our analysis suggests that the Gutenberg‐Richter relation originates from Coulomb stress fluctuations caused by elastic rock heterogeneity.
Key Points
Elastic heterogeneity causes strong Coulomb stress fluctuation of power law type
Gutenberg‐Richter relation results from power law fluctuations of Coulomb stress
Universal fractal nature of elastic heterogeneity suggests a universal b value
A method to directly determine the Wilson coefficients for rare b → s transitions using B0 → K∗0μ+μ− decays in an unbinned maximum likelihood fit is presented. The method has several advantages ...compared to the conventional determination of the Wilson coefficients from angular observables that are determined in bins of q2, the square of the mass of the dimuon system. The method uses all experimental information in a more efficient way and automatically accounts for experimental correlations. Performing pseudoexperiments, we show the improved sensitivity of the proposed method for the Wilson coefficients. We also demonstrate that it will be possible to use the method with the combined Run 1 and 2 data sample taken by the LHCb experiment.
A
bstract
A method to directly determine the Wilson coefficients for rare
b
→
s
transitions using
B
0
→
K
∗0
μ
+
μ
−
decays in an unbinned maximum likelihood fit is presented. The method has several ...advantages compared to the conventional determination of the Wilson coefficients from angular observables that are determined in bins of
q
2
, the square of the mass of the dimuon system. The method uses all experimental information in a more efficient way and automatically accounts for experimental correlations. Performing pseudoexperiments, we show the improved sensitivity of the proposed method for the Wilson coefficients. We also demonstrate that it will be possible to use the method with the combined Run 1 and 2 data sample taken by the LHCb experiment.
The German National Analysis Facility (NAF) was set up at DESY, starting end of 2007 in the context of the Helmholtz Alliance "Physics at the Terascale". The NAF complements the DESY and the German ...Grid resources, and hence offers users from the German HEP institutes the best possible environment for data analysis. In the first part, the key aspects and components of the NAF are briefly presented with an emphasis on recent improvements. In the second part, the use cases of the three participating LHC experiments, ATLAS, CMS and LHCb, will be presented. Differences and commonalities in the usage of the NAF will be shown. Special emphasis will be placed on the usage of PROOF, whose usage on the NAF has been pioneered by CMS. It is now adapted by ATLAS. The third part will concentrate on how the NAF was used for detector optimisation studies in the preparation of one of the ILC Lol's (ILD 2009), as well as how CALICE uses the NAF for the analysis of their data taken in several test beam experiments performed for detector R & D. Finally, future developments of the NAF are presented.
This paper presents the design of the LHCb trigger and its performance on data taken at the LHC in 2011. A principal goal of LHCb is to perform flavour physics measurements, and the trigger is ...designed to distinguish charm and beauty decays from the light quark background. Using a combination of lepton identification and measurements of the particles' transverse momenta the trigger selects particles originating from charm and beauty hadrons, which typically fly a finite distance before decaying. The trigger reduces the roughly 11MHz of bunch-bunch crossings that contain at least one inelastic pp interaction to 3 kHz. This reduction takes place in two stages; the first stage is implemented in hardware and the second stage is a software application that runs on a large computer farm. A data-driven method is used to evaluate the performance of the trigger on several charm and beauty decay modes.
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