In the Tau section of the HFLAV 2023 report (arXiv:2411.18639 [hep-ex]) we present an improved global fit of the tau branching fractions and new combinations of tau lepton-flavour-violating (LFV) upper limits. The branching fraction fit includes recent measurements and furthermore since this report features nuisance fit parameters. The HFLAV fit is now...
Charged Lepton Flavour Violation (cLFV) is strongly suppressed in the Standard Model and therefore represents a sensitive probe for physics beyond it. Recently, the LHCb experiment has performed dedicated searches for cLFV, both in semileptonic b-hadron decays and in purely leptonic tau decays, placing competitive bounds on several decay modes. These results provide relevant constraints on a...
Upgrading the SuperKEKB e+e− collider with polarized electron beams, the Chiral Belle project, provides new and unique opportunities for searches for new physics via precision electroweak and other measurements, including measurements involving the tau lepton.
These include measurements the neutral current vector couplings via left-right asymmetry (ALR) measurements in annihilations to pairs...
Neutrino non-standard interactions (NSI) have been studied in a variety of contexts and suggested as a possible mechanism for resolving certain unexpected results in oscillation experiments. NSI may be generated in various ways and take a variety of forms. We focus on flavor-changing neutral current NSIs involving tau neutrinos. In simple scenarios in which these are generated by...
The existence and unknown nature of dark matter motivates dark sector searches at accelerators. The Belle experiment has collected samples of $e^{+}e^{-}$ collision data containing a huge number of $e^{+}e^{-} \rightarrow \tau^{+}\tau^{-}$ events with constrained kinematics and low backgrounds, enabling several world-leading dark matter searches in the sub-GeV mass region. Using 800...
We estimate the precision at FCC-ee on the measurements of the tau mass, lifetime, leptonic branching fractions, and on the searches for lepton-flavour-violating branching fractions $\tau \to \mu\gamma$ and $\tau \to 3\mu$. We compute the estimated precision on the lepton flavour universality tests, considering the 2nd-order QED radiative corrections and estimating the radiative corrections...
In the SM, the electroweak bosons couple to the three lepton families with the same strength having the only difference in their behaviour due to the difference in mass. The current measurements of the ratios of branching fractions for b-hadrons decaying into final states with different lepton flavours deviate of the order of 3 σ with respect to the Standar Model. This talk presents recent...
In this talk we present the outcome of a stand-alone feasibility study using RapidSim simulation software that demonstrates that the Large Hadron Collider beauty (LHCb) experiment will be capable of observing the decays $B^+\rightarrow\tau^+\nu_{\tau}$ and $B_c^+\rightarrow\tau^+\nu_{\tau}$ using the data that is being collecting during Run 3 of the LHC. Our proposed analysis exploits the...
More then a decade ago, the BaBar experiment measured a 2.8$\sigma$ deviation from the Standard Model when searching for CP violation in $\tau^{-} \to \pi^{-} K_{S}^{0} (\geq 0 \pi^{0}) \nu_{\tau}$ decays.
Since then, the Tau Physics community has eagerly anticipated a new measurement. The first run of the Belle II experiment collected a 365 fb$^{-1}$ sample of $e^{+}e^{-}$ collisions at a...
The $\tau$ lifetime is a fundamental parameter in the Standard Model, providing an important contribution to the test of lepton-flavour universality. The first run of the Belle II experiment collected a 365 fb$^{-1}$ sample of $e^{+}e^{-}$ collisions at a centre-of-mass energy corresponding to the $\Upsilon(4S)$ resonance, delivering around 340 million $e^{+}e^{-} \rightarrow...
A measurement of the key cross section e+e- to pi+pi- for hadronic vacuum polarization (HVP)is presented with the full BABAR statistics using a new method not relying on particle ID to separate pions ans muons, therefore independent from the 2009 analysis. This result should play an important role to clarify the presently rather confused situation where large discrepancies are observed between...
We discuss recent results leading to a new understanding of one of the two
main approaches to determining $\alpha_s$ from finite-energy sum rule analyses of non-strange hadronic $\tau$ decay data. This approach involves fits to sets of differently weighted spectral integrals with a single common upper endpoint, $s=s_0$, in which several in-principle-present, higher-dimension condensate...
This contribution presents recent results from the CMS experiment at the LHC on searches for Lepton Flavor Violation (LFV) and Lepton Flavor Universality (LFU) violation in heavy flavour decays involving tau leptons. The tau acts as a powerful probe for physics beyond the Standard Model (BSM), particularly in the low transverse momentum (p_T) regime typical of B hadron decays. We report on a...
Several discrepant measurements have been observed by LHCb and other experiments in b→cτν decays over the past few years. If these are due to new physics beyond the Standard Model, several models suggest an associated large enhancement in the branching fractions of b→sττ decays. Such decays have not been observed yet, and the existing upper limits which have been set are several orders of...
The H->tau tau decay mode has a relatively high BR and good S/B ratio when considering advanced techniques to reconstruct and identify tau leptons in all possible decay modes. This enables the search of rare process, as non-resonant di-Higgs production, where one of the Higgs boson decays to ditaus. Possible channels involve H->gamma gamma, H->bb, associated with the H->tau tau decay. This...
The rates of lepton-flavour violation in charged lepton decays are enhanced in many beyond-the-standard-model theories. During the first run of the Belle II experiment 365 fb$^{-1}$ of $e^{+}e^{-}$ collision data was collected at a centre-of-mass energy corresponding to the $\Upsilon(4S)$ resonance. This dataset contains around 340 million $e^{+}e^{-} \rightarrow \tau^{+}\tau^{-}$ events with...
The rates of lepton-flavour, lepton-number, and baryon-number violating $\tau$ decays are enhanced in many beyond-the-standard-model theories. The Belle and Belle II experiments have collected samples of $e^{+}e^{-}$ collision data containing a huge number of $e^{+}e^{-} \rightarrow \tau^{+}\tau^{-}$ events with constrained kinematics and low backgrounds, providing an ideal environment to...
The Belle and Belle II experiments have collected a $1.1~\mathrm{ab}^{-1}$ sample of $e^+e^-$ collision data at centre-of-mass energies corresponding to the $\Upsilon(4S)$ resonances. The $\Upsilon(4S)$ resonance decays almost exclusively to $B\bar{B}$ pairs. Using these data, we search for lepton-flavour-violating decays $B\to K^{(*)}\tau \ell$. In addition, we present searches for...
Many extensions of the Standard Model predict new phenomena like beyond-the-Standard-Model couplings to the Higgs boson, charged Higgs, Heavy neutral lepton, supersymmetry, among others. In this talk, the latest searches latest from the ATLAS experiment will be reported, with emphasis on the final states using special tau reconstruction techniques like merged or boosted tau topologies as well...
Many theories beyond the Standard Model predict new phenomena, such as leptoquarks, vector like leptons, supersymmetry, new scalars or heavy leptons, in final states with isolated taus reconstructed using standard techniques. Searches for new physics with such signatures, produced either resonantly or non-resonantly, are performed using the ATLAS experiment at the LHC. The most recent results...
Present day high statistic tau lepton experimental samples, require continuous revision of simulation precision. This is especially important for multi-dimensional signatures. That is in partiucular important in context of anomalous couplings.
Also, because evolution of software environments, completion of programs migration to C++ as well as study of new effects become of ever greater...
The SND@LHC experiment was designed to perform measurements with neutrinos produced at the LHC within the unexplored pseudo-rapidity range of 7.2 < 𝜂 < 8.6. Located 480 m downstream of IP1 in the unused TI18 tunnel, this compact and stand-alone experiment employs a hybrid detector system consisting of 800 kg of tungsten plates interleaved with emulsion and electronic trackers, complemented by...
Water Cherenkov detectors have demonstrated exceptional sensitivity in
neutrino observation over the years. The Hyper-Kamiokande (Hyper-K),
the third generation of underground detectors in Japan, represents a
significant advancement in both sensitivity and scalability. Hyper-K will
act as the far detector for a long-baseline neutrino oscillation experiment
using the upgraded 1.3 MW J-PARC...
The MUonE experiment at CERN aims to provide an independent measurement of the leading-order hadronic contribution to the muon g-2 ($a_{\mu}^\text{HVP}$), complementary to the existing ones. The innovative approach proposed by MUonE is based on the measurement of the hadronic contribution to the running of the QED coupling, which can be extracted from a precise measurement of the shape of the...
The super tau-charm facility proposed in China, is suppose to produce 3.5 billion tau pairs per year in the energy region of 4 to 5 GeV. Besides, the STCF covers the threshold of tau pairs. Based on thses samples, general topics are proposed at STCF, e.g., cLFV processes, $|V_{us}|$ measurements, alpha_s and tau mass measurements. Novel topics are proposed at well, e.g., tau atoms. In this...
The High-Luminosity LHC (HL-LHC) will pose significant challenges for the reliable and accurate reconstruction and identification of physics objects in the High-Level Trigger (HLT) of the CMS experiment, particularly in the presence of up to 200 simultaneous proton-proton interactions per event. The upgraded CMS detector will feature the High-Granularity Calorimeter (HGCAL), offering...
The Mu2e experiment will search for coherent neutrinoless conversion of a negative muon into an electron in the field of an aluminium nucleus. Observation of this process would be a signature of Charged Lepton Flavor Violation (CLFV), a Beyond the Standard Model (BSM) process predicted by various theories. Mu2e aims to improve the current limit by four orders of magnitude, reaching a single...
