Jet reconstruction with the LHCb calorimeters in future upgrades Ricostruzione dei jet con i futuri calorimetri di LHCb

Performance evaluation of jet reconstruction quality in LHCb for Z -> b bbar channel in different configurations: nominal Run 3 configuration and with HCAL calorimeter swapped for an inert target. A multivariate model for the JEC function was built and used to compute transverse momentum resolution in both cases. The same model was used to evaluate jet reconstruction efficiency and jet fake probability. Further study done for JES and resolution systematic uncertainty based on Run 2 data. Valutazione delle prestazioni di ricostruzione dei jet in LHCb per il processo Z -> b bbar in due differenti configurazioni: configurazione nominale di Run 3 e configurazione con calorimetro adronico HCAL sostituito con un assorbitore passivo. Per lo studio delle prestazioni si è costruito un modello multivariabile della JEC, questo modello è poi stato utilizzato per stimare la risoluzione sull'impulso trasverso dei jet nei due casi. Lo stesso modello JEC è stato usato per la stima dell'efficienza di ricostruzione e della probabilità di misidentificazione. Studio ulteriore delle incertezze sistematiche di JES e risoluzione a partire da dati di Run 2.ope

Jet reconstruction with the LHCb calorimeters in future upgrades Ricostruzione dei jet con i futuri calorimetri di LHCb

Performance evaluation of jet reconstruction quality in LHCb for Z -> b bbar channel in different configurations: nominal Run 3 configuration and with HCAL calorimeter swapped for an inert target. A multivariate model for the JEC function was built and used to compute transverse momentum resolution in both cases. The same model was used to evaluate jet reconstruction efficiency and jet fake probability. Further study done for JES and resolution systematic uncertainty based on Run 2 data. Valutazione delle prestazioni di ricostruzione dei jet in LHCb per il processo Z -> b bbar in due differenti configurazioni: configurazione nominale di Run 3 e configurazione con calorimetro adronico HCAL sostituito con un assorbitore passivo. Per lo studio delle prestazioni si è costruito un modello multivariabile della JEC, questo modello è poi stato utilizzato per stimare la risoluzione sull'impulso trasverso dei jet nei due casi. Lo stesso modello JEC è stato usato per la stima dell'efficienza di ricostruzione e della probabilità di misidentificazione. Studio ulteriore delle incertezze sistematiche di JES e risoluzione a partire da dati di Run 2

Search for leptonic decays of the dark photon at NA62

International audienceThe NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of $1.4\times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV$/c^2$ and coupling values in the range $10^{-6}$ to $4\times10^{-5}$. An interpretation of the $e^+ e^-$ search result in terms of the emission and decay of an axion-like particle is also presented

Search for leptonic decays of the dark photon at NA62

The NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of $1.4 \times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV/$c^2$ and coupling values in the range $10^{−6}$ to $4 \times 10^{−5}$. An interpretation of the $e^+ e^−$ search result in terms of the emission and decay of an axion-like particle is also presented.The NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of $1.4\times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV$/c^2$ and coupling values in the range $10^{-6}$ to $4\times10^{-5}$. An interpretation of the $e^+ e^-$ search result in terms of the emission and decay of an axion-like particle is also presented

Search for dark photon decays to μ+μ−\mu^+\mu^- at NA62

International audienceThe NA62 experiment at CERN, designed to study the ultra-rare decay $K^+ \to \pi^+\nu\overline{\nu}$, has also collected data in beam-dump mode. In this configuration, dark photons may be produced by protons dumped on an absorber and reach a decay volume beginning 80 m downstream. A search for dark photons decaying in flight to $\mu^+\mu^-$ pairs is reported, based on a sample of $1.4 \times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. A region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon masses between 215 and 550 MeV$/c^2$

Search for leptonic decays of the dark photon at NA62

International audienceThe NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of $1.4\times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV$/c^2$ and coupling values in the range $10^{-6}$ to $4\times10^{-5}$. An interpretation of the $e^+ e^-$ search result in terms of the emission and decay of an axion-like particle is also presented

Development of a new CEDAR for kaon identification at the NA62 experiment at CERN

International audienceThe NA62 experiment at CERN utilises a differential Cherenkov counter with achromatic ring focus (CEDAR) for tagging kaons within an unseparated monochromatic beam of charged hadrons. The CEDAR-H detector was developed to minimise the amount of material in the path of the beam by using hydrogen gas as the radiator medium. The detector was shown to satisfy the kaon tagging requirements in a test-beam before installation and commissioning at the experiment. The CEDAR-H performance was measured using NA62 data collected in 2023

Development of a new CEDAR for kaon identification at the NA62 experiment at CERN

International audienceThe NA62 experiment at CERN utilises a differential Cherenkov counter with achromatic ring focus (CEDAR) for tagging kaons within an unseparated monochromatic beam of charged hadrons. The CEDAR-H detector was developed to minimise the amount of material in the path of the beam by using hydrogen gas as the radiator medium. The detector was shown to satisfy the kaon tagging requirements in a test-beam before installation and commissioning at the experiment. The CEDAR-H performance was measured using NA62 data collected in 2023

Search for K+K^+ decays into the π+e+e−e+e−\pi^+e^+e^-e^+e^- final state

International audienceThe first search for ultra-rare $K^+$ decays into the $\pi^+e^+e^-e^+e^-$ final state is reported, using a dataset collected by the NA62 experiment at CERN in 2017-2018. An upper limit of $1.4\times 10^{-8}$ at 90% CL is obtained for the branching ratio of the $K^+\to\pi^+e^+e^-e^+e^-$ decay, predicted in the Standard Model to be $(7.2\pm0.7)\times 10^{-11}$. Upper limits at 90% CL are obtained at the level of $10^{-9}$ for the branching ratios of two prompt decay chains involving pair-production of hidden-sector mediators: $K^+\to\pi^+aa$, $a\to e^+e^-$ and $K^+\to\pi^+S$, $S\to A^\prime A^\prime$, $A^\prime\to e^+e^-$. The QCD axion is excluded as a possible explanation of the "17 MeV anomaly"

Measurement of the K+→π+γγK^+\to\pi^+\gamma\gamma decay

International audienceA sample of 3984 candidates of the $K^+\to\pi^+\gamma\gamma$ decay, with an estimated background of $291\pm14$ events, was collected by the NA62 experiment at CERN during 2017-2018. In order to describe the observed di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be $(9.61\pm0.17)\times10^{-7}$. The first search for production and prompt decay of an axion-like particle with gluon coupling in the process $K^+\to\pi^+a$, $a\to\gamma\gamma$ is also reported