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H Abramowicz - One of the best experts on this subject based on the ideXlab platform.
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search for type iii seesaw heavy Leptons in diLepton final states in pp collisions at sqrt s 13 tev with the atlas detector
European Physical Journal C, 2021Co-Authors: G Aad, B Abbott, Nicola Louise Abraham, S H Abidi, O S Abouzeid, D C Abbott, Abed A Abud, K Abeling, D K Abhayasinghe, H AbramowiczAbstract:A search for the pair production of heavy Leptons as predicted by the type-III seesaw mechanism is presented. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to 139 fb$^{-1}$ of integrated luminosity recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis focuses on the final state with two light Leptons (electrons or muons) of different flavour and charge combinations, with at least two jets and large missing transverse momentum. No significant excess over the Standard Model expectation is observed. The results are translated into exclusion limits on heavy-Lepton masses, and the observed lower limit on the mass of the type-III seesaw heavy Leptons is 790 GeV at 95% confidence level.
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search for supersymmetry in events with four or more Leptons in s 13 tev pp collisions with atlas
Physical Review D, 2018Co-Authors: M Aaboud, B Abbott, Ovsat Abdinov, G Aad, Nicola Louise Abraham, B Abeloos, S H Abidi, O S Abouzeid, H AbramowiczAbstract:Results from a search for supersymmetry in events with four or more charged Leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb-1 of proton-proton collisions delivered by the Large Hadron Collider at s=13 TeV and recorded by the ATLAS detector. Four-Lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits are set at the 95% confidence level in simplified models of general gauge mediated supersymmetry, where Higgsino masses are excluded up to 295 GeV. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to charged Leptons, lower limits of 1.46, 1.06, and 2.25 TeV are placed on wino, sLepton and gluino masses, respectively. © 2018 CERN.
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probing Lepton flavour violation via neutrinoless decays with the atlas detector
European Physical Journal C, 2016Co-Authors: G Aad, B Abbott, H. Abreu, Ovsat Abdinov, M. Abolins, J Abdallah, R Aben, H Abramowicz, O S Abouzeid, R AbreuAbstract:This article presents the sensitivity of the ATLAS experiment to the Lepton-flavour-violating decays of . A method utilising the production of Leptons via decays is used. This method is applied to the sample of 20.3 fb of pp collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC in 2012. No event is observed passing the selection criteria, and the observed (expected) upper limit on the Lepton branching fraction into three muons, , is () at 90 % confidence level.
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probing Lepton flavour violation via neutrinoless formula see text decays with the atlas detector
European Physical Journal C, 2016Co-Authors: G Aad, B Abbott, H. Abreu, Ovsat Abdinov, M. Abolins, J Abdallah, R Aben, H Abramowicz, O S Abouzeid, R AbreuAbstract:This article presents the sensitivity of the ATLAS experiment to the Lepton-flavour-violating decays of [Formula: see text]. A method utilising the production of [Formula: see text] Leptons via [Formula: see text] decays is used. This method is applied to the sample of 20.3 fb[Formula: see text] of pp collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC in 2012. No event is observed passing the selection criteria, and the observed (expected) upper limit on the [Formula: see text] Lepton branching fraction into three muons, [Formula: see text], is [Formula: see text] ([Formula: see text]) at 90 % confidence level.
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search for new phenomena in events with three or more charged Leptons in pp collisions at s 8 tev with the atlas detector
Journal of High Energy Physics, 2015Co-Authors: G Aad, B. Abi, B Abbott, Ovsat Abdinov, M. Abolins, J Abdallah, R Aben, O S Abouzeid, Abdel S Khalek, H AbramowiczAbstract:A generic search for anomalous production of events with at least three charged Leptons is presented. The data sample consists of pp collisions at TeV collected in 2012 by the ATLAS experiment at the CERN Large Hadron Collider, and corresponds to an integrated luminosity of 20.3 fb(-1). Events are required to have at least three selected Lepton candidates, at least two of which must be electrons or muons, while the third may be a hadronically decaying tau. Selected events are categorized based on their Lepton flavour content and signal regions are constructed using several kinematic variables of interest. No significant deviations from Standard Model predictions are observed. Model-independent upper limits on contributions from beyond the Standard Model phenomena are provided for each signal region, along with prescription to re-interpret the limits for any model. Constraints are also placed on models predicting doubly charged Higgs bosons and excited Leptons. For doubly charged Higgs bosons decaying to e tau or mu tau, lower limits on the mass are set at 400 GeV at 95% confidence level. For excited Leptons, constraints are provided as functions of both the mass of the excited state and the compositeness scale I >, with the strongest mass constraints arising in regions where the mass equals I >. In such scenarios, lower mass limits are set at 3.0 TeV for excited electrons and muons, 2.5 TeV for excited taus, and 1.6 TeV for every excited-neutrino flavour.
G Aad - One of the best experts on this subject based on the ideXlab platform.
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search for type iii seesaw heavy Leptons in diLepton final states in pp collisions at sqrt s 13 tev with the atlas detector
European Physical Journal C, 2021Co-Authors: G Aad, B Abbott, Nicola Louise Abraham, S H Abidi, O S Abouzeid, D C Abbott, Abed A Abud, K Abeling, D K Abhayasinghe, H AbramowiczAbstract:A search for the pair production of heavy Leptons as predicted by the type-III seesaw mechanism is presented. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to 139 fb$^{-1}$ of integrated luminosity recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis focuses on the final state with two light Leptons (electrons or muons) of different flavour and charge combinations, with at least two jets and large missing transverse momentum. No significant excess over the Standard Model expectation is observed. The results are translated into exclusion limits on heavy-Lepton masses, and the observed lower limit on the mass of the type-III seesaw heavy Leptons is 790 GeV at 95% confidence level.
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test of the universality of tau and mu Lepton couplings in w boson decays from t bar t events with the atlas detector
2020Co-Authors: G Aad, A Kupco, K Jakobs, M Spousta, M Cobal, Jay Chan, T Dreyer, Yufeng Wang, Peilong Wang, Stefan SchmittAbstract:The Standard Model of particle physics encapsulates our current best understanding of physics at the smallest scales. A fundamental axiom of this theory is the universality of the couplings of the different generations of Leptons to the electroweak gauge bosons. The measurement of the ratio of the rate of decay of $W$ bosons to $\tau$-Leptons and muons, $R(\tau/\mu) = B(W \to \tau \nu_\tau)/B(W \to \mu \nu_\mu)$, constitutes an important test of this axiom. A measurement of this quantity with a novel technique using di-Leptonic $t\bar{t}$ events is presented based on 139 fb${}^{-1}$ of data recorded with the ATLAS detector in proton--proton collisions at $\sqrt{s}=13$ TeV. Muons originating from $W$ bosons and those originating from an intermediate $\tau$-Lepton are distinguished using the lifetime of the $\tau$-Lepton, through the muon transverse impact parameter, and differences in the muon transverse momentum spectra. The value of $R(\tau/\mu)$ is found to be $0.992 \pm 0.013 [\pm 0.007 (stat) \pm 0.011 (syst)]$ and is in agreement with the hypothesis of universal Lepton couplings as postulated in the Standard Model. This is the most precise measurement of this ratio, and the only such measurement from the Large Hadron Collider, to date.
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search for direct stau production in events with two hadronic τ Leptons in s 13 tev pp collisions with the atlas detector
Physical Review D, 2020Co-Authors: G Aad, B Abbott, S H Abidi, O S Abouzeid, D C Abbott, Abed A Abud, K Abeling, D K Abhayasinghe, Nicola Louise AbrahamAbstract:A search for the direct production of the supersymmetric partners of τ-Leptons (staus) in final states with two hadronically decaying τ-Leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of 139 fb-1, recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected Standard Model background is observed. Limits are derived in scenarios of direct production of stau pairs with each stau decaying into the stable lightest neutralino and one τ-Lepton in simplified models where the two stau mass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidence level for a massless lightest neutralino.
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search for supersymmetry in events with four or more Leptons in s 13 tev pp collisions with atlas
Physical Review D, 2018Co-Authors: M Aaboud, B Abbott, Ovsat Abdinov, G Aad, Nicola Louise Abraham, B Abeloos, S H Abidi, O S Abouzeid, H AbramowiczAbstract:Results from a search for supersymmetry in events with four or more charged Leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb-1 of proton-proton collisions delivered by the Large Hadron Collider at s=13 TeV and recorded by the ATLAS detector. Four-Lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits are set at the 95% confidence level in simplified models of general gauge mediated supersymmetry, where Higgsino masses are excluded up to 295 GeV. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to charged Leptons, lower limits of 1.46, 1.06, and 2.25 TeV are placed on wino, sLepton and gluino masses, respectively. © 2018 CERN.
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probing Lepton flavour violation via neutrinoless decays with the atlas detector
European Physical Journal C, 2016Co-Authors: G Aad, B Abbott, H. Abreu, Ovsat Abdinov, M. Abolins, J Abdallah, R Aben, H Abramowicz, O S Abouzeid, R AbreuAbstract:This article presents the sensitivity of the ATLAS experiment to the Lepton-flavour-violating decays of . A method utilising the production of Leptons via decays is used. This method is applied to the sample of 20.3 fb of pp collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC in 2012. No event is observed passing the selection criteria, and the observed (expected) upper limit on the Lepton branching fraction into three muons, , is () at 90 % confidence level.
A M Sirunyan - One of the best experts on this subject based on the ideXlab platform.
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search for an excited Lepton that decays via a contact interaction to a Lepton and two jets in proton proton collisions at s 13 tev
Journal of High Energy Physics, 2020Co-Authors: A M Sirunyan, A Tumasyan, W Adam, T Bergauer, J Brandstetter, M Dragicevic, J Ero, Federico Ambrogi, Escalante A Del Valle, Martin FlechlAbstract:Results are presented from a search for events containing an excited Lepton (electron or muon) produced in association with an ordinary Lepton of the same flavor and decaying to a Lepton and two hadronic jets. Both the production and the decay of the excited Leptons are assumed to occur via a contact interaction with a characteristic energy scale Λ. The branching fraction for the decay mode under study increases with the mass of the excited Lepton and is the most sensitive channel for very heavy excited Leptons. The analysis uses a sample of proton-proton collisions collected by the CMS experiment at the LHC at $$ \sqrt{s} $$ = 13 TeV, corresponding to an integrated luminosity of 77.4 fb−1. The four-body invariant mass of the two Lepton plus two jet system is used as the primary discriminating variable. No significant excess of events beyond the expectation for standard model processes is observed. Assuming that Λ is equal to the mass of the excited Leptons, excited electrons and muons with masses below 5.6 and 5.7 TeV, respectively, are excluded at 95% confidence level. These are the best limits to date.
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search for direct pair production of supersymmetric partners to the τ Lepton in proton proton collisions at s 13tev
European Physical Journal C, 2020Co-Authors: A M Sirunyan, A Tumasyan, W Adam, T Bergauer, J Brandstetter, M Dragicevic, J Ero, Federico Ambrogi, Escalante A Del Valle, Martin FlechlAbstract:A search is presented for $\tau$ sLepton pairs produced in proton-proton collisions at a center-of-mass energy of 13 TeV. The search is carried out in events containing two $\tau$ Leptons in the final state, on the assumption that each $\tau$ sLepton decays primarily to a $\tau$ Lepton and a neutralino. Events are considered in which each $\tau$ Lepton decays to one or more hadrons and a neutrino, or in which one of the $\tau$ Leptons decays instead to an electron or a muon and two neutrinos. The data, collected with the CMS detector in 2016 and 2017, correspond to an integrated luminosity of 77.2 fb$^{-1}$. The observed data are consistent with the standard model background expectation. The results are used to set 95% confidence level upper limits on the cross section for $\tau$ sLepton pair production in various models for $\tau$ sLepton masses between 90 and 200 GeV and neutralino masses of 1, 10, and 20 GeV. In the case of purely left-handed $\tau$ sLepton production and decay to a $\tau$ Lepton and a neutralino with a mass of 1 GeV, the strongest limit is obtained for a $\tau$ sLepton mass of 125 GeV at a factor of 1.14 larger than the theoretical cross section.
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search for vectorlike Leptons in multiLepton final states in proton proton collisions at s 13 tev
Physical Review D, 2019Co-Authors: A M Sirunyan, A Tumasyan, W Adam, T Bergauer, J Brandstetter, M Dragicevic, J Ero, Federico Ambrogi, Escalante A Del Valle, Martin FlechlAbstract:A search for vectorlike Leptons in multiLepton final states is presented. The data sample corresponds to an integrated luminosity of 77.4 fb(-1) of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2016 and 2017. Events are categorized by the multiplicity of electrons, muons, and hadronically decaying tau Leptons. The missing transverse momentum and the scalar sum of the Lepton transverse momenta are used to distinguish the signal from background. The observed results are consistent with the expectations from the standard model hypothesis. The existence of a vectorlike Lepton doublet, coupling to the third-generation standard model Leptons in the mass range of 120-790 GeV, is excluded at 95% confidence level. These are the most stringent limits yet on the production of a vectorlike Lepton doublet, coupling to the third-generation standard model Leptons.
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search for supersymmetry with a compressed mass spectrum in the vector boson fusion topology with 1 Lepton and 0 Lepton final states in proton proton collisions at s 13 tev
Journal of High Energy Physics, 2019Co-Authors: A M Sirunyan, A Tumasyan, W Adam, E Asilar, T Bergauer, J Brandstetter, M Dragicevic, Federico Ambrogi, Escalante A Del Valle, Martin FlechlAbstract:A search for supersymmetric particles produced in the vector boson fusion topology in proton-proton collisions is presented. The search targets final states with one or zero Leptons, large missing transverse momentum, and two jets with a large separation in rapidity. The data sample corresponds to an integrated luminosity of 35.9 fb$^{−1}$ of proton-proton collisions at $ \sqrt{s} $ = 13 TeV collected in 2016 with the CMS detector at the LHC. The observed dijet invariant mass and Lepton-neutrino transverse mass spectra are found to be consistent with the standard model predictions. Upper limits are set on the cross sections for chargino $ \left({\tilde{\upchi}}_1^{\pm}\right) $ and neutralino $ \left({\tilde{\upchi}}_2^0\right) $ production with two associated jets. For a compressed mass spectrum scenario in which the $ {\tilde{\upchi}}_1^{\pm } $ and $ {\tilde{\upchi}}_2^0 $ decays proceed via a light sLepton and the mass difference between the lightest neutralino $ {\tilde{\upchi}}_1^0 $ and the mass-degenerate particles $ {\tilde{\upchi}}_1^{\pm } $ and $ {\tilde{\upchi}}_2^0 $ is 1 (30) GeV, the most stringent lower limit to date of 112 (215) GeV is set on the mass of these latter two particles.
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search for excited Leptons in llγ final states in proton proton collisions at s 13 tev
Journal of High Energy Physics, 2019Co-Authors: A M Sirunyan, A Tumasyan, W Adam, E Asilar, T Bergauer, J Brandstetter, M Dragicevic, J Ero, F Ambrogi, Escalante A Del ValleAbstract:A search is presented for excited electrons and muons in llγ final states at the LHC. The search is based on a data sample corresponding to an integrated luminosity of 35.9 fb$^{−1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector in 2016. This is the first search for excited Leptons at $ \sqrt{s} $ = 13 TeV. The observation is consistent with the standard model background prediction, and the most stringent exclusion limits to date are set on the excited Lepton mass and the compositeness scale, at 95% confidence level. Excited electrons and muons are excluded for masses below 3.9 and 3.8 TeV, respectively, under the assumption that the excited Lepton mass equals the compositeness scale. The best observed limit on the compositeness scale is obtained with an excited Lepton mass of around 1.0 TeV, excluding values below 25 TeV for both excited electrons and muons.
B Abbott - One of the best experts on this subject based on the ideXlab platform.
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search for type iii seesaw heavy Leptons in diLepton final states in pp collisions at sqrt s 13 tev with the atlas detector
European Physical Journal C, 2021Co-Authors: G Aad, B Abbott, Nicola Louise Abraham, S H Abidi, O S Abouzeid, D C Abbott, Abed A Abud, K Abeling, D K Abhayasinghe, H AbramowiczAbstract:A search for the pair production of heavy Leptons as predicted by the type-III seesaw mechanism is presented. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to 139 fb$^{-1}$ of integrated luminosity recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis focuses on the final state with two light Leptons (electrons or muons) of different flavour and charge combinations, with at least two jets and large missing transverse momentum. No significant excess over the Standard Model expectation is observed. The results are translated into exclusion limits on heavy-Lepton masses, and the observed lower limit on the mass of the type-III seesaw heavy Leptons is 790 GeV at 95% confidence level.
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search for direct stau production in events with two hadronic τ Leptons in s 13 tev pp collisions with the atlas detector
Physical Review D, 2020Co-Authors: G Aad, B Abbott, S H Abidi, O S Abouzeid, D C Abbott, Abed A Abud, K Abeling, D K Abhayasinghe, Nicola Louise AbrahamAbstract:A search for the direct production of the supersymmetric partners of τ-Leptons (staus) in final states with two hadronically decaying τ-Leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of 139 fb-1, recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected Standard Model background is observed. Limits are derived in scenarios of direct production of stau pairs with each stau decaying into the stable lightest neutralino and one τ-Lepton in simplified models where the two stau mass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidence level for a massless lightest neutralino.
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search for supersymmetry in events with four or more Leptons in s 13 tev pp collisions with atlas
Physical Review D, 2018Co-Authors: M Aaboud, B Abbott, Ovsat Abdinov, G Aad, Nicola Louise Abraham, B Abeloos, S H Abidi, O S Abouzeid, H AbramowiczAbstract:Results from a search for supersymmetry in events with four or more charged Leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb-1 of proton-proton collisions delivered by the Large Hadron Collider at s=13 TeV and recorded by the ATLAS detector. Four-Lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits are set at the 95% confidence level in simplified models of general gauge mediated supersymmetry, where Higgsino masses are excluded up to 295 GeV. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to charged Leptons, lower limits of 1.46, 1.06, and 2.25 TeV are placed on wino, sLepton and gluino masses, respectively. © 2018 CERN.
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probing Lepton flavour violation via neutrinoless decays with the atlas detector
European Physical Journal C, 2016Co-Authors: G Aad, B Abbott, H. Abreu, Ovsat Abdinov, M. Abolins, J Abdallah, R Aben, H Abramowicz, O S Abouzeid, R AbreuAbstract:This article presents the sensitivity of the ATLAS experiment to the Lepton-flavour-violating decays of . A method utilising the production of Leptons via decays is used. This method is applied to the sample of 20.3 fb of pp collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC in 2012. No event is observed passing the selection criteria, and the observed (expected) upper limit on the Lepton branching fraction into three muons, , is () at 90 % confidence level.
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probing Lepton flavour violation via neutrinoless formula see text decays with the atlas detector
European Physical Journal C, 2016Co-Authors: G Aad, B Abbott, H. Abreu, Ovsat Abdinov, M. Abolins, J Abdallah, R Aben, H Abramowicz, O S Abouzeid, R AbreuAbstract:This article presents the sensitivity of the ATLAS experiment to the Lepton-flavour-violating decays of [Formula: see text]. A method utilising the production of [Formula: see text] Leptons via [Formula: see text] decays is used. This method is applied to the sample of 20.3 fb[Formula: see text] of pp collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC in 2012. No event is observed passing the selection criteria, and the observed (expected) upper limit on the [Formula: see text] Lepton branching fraction into three muons, [Formula: see text], is [Formula: see text] ([Formula: see text]) at 90 % confidence level.
A M Bykov - One of the best experts on this subject based on the ideXlab platform.
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gev tev cosmic ray Leptons in the solar system from the bow shock wind nebula of the nearest millisecond pulsar j0437 4715
The Astrophysical Journal, 2019Co-Authors: A M Bykov, A E Petrov, A M Krassilchtchikov, K P Levenfish, S M Osipov, G G PavlovAbstract:We consider acceleration of Leptons up to GeV-TeV energies in the bow shock wind nebula of PSR J0437-4715 and their subsequent diffusion through the interstellar magnetic fields. The Leptons accelerated at the pulsar wind termination surface are injected into re-acceleration in colliding shock flows. Modelled spectra of synchrotron emission from the accelerated electrons and positrons are consistent with the far-ultraviolet and X-ray observations of the nebula carried out with the Hubble Space Telescope and Chandra X-ray Observatory. These observations are employed to constrain the absolute fluxes of relativistic Leptons, which are escaping from the nebula and eventually reaching the Solar System after energy-dependent diffusion through the local interstellar medium accompanied by synchrotron and Compton losses. It is shown that accelerated Leptons from the nebula of PSR J0437-4715 can be responsible both for the enhancement of the positron fraction above a few GeV detected by PAMELA and AMS-02 spectrometers and for the TeV range Lepton fluxes observed with H.E.S.S., VERITAS, Fermi, CALET, and DAMPE.
