K. Ehatäht

We present a feasibility study to probe quantum entanglement and Bell inequality violation in the process ${\mathrm{e}}^{+}{\mathrm{e}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ at a center-of-mass energy of $\sqrt{s}=10.579\text{ }\text{ }\mathrm{GeV}$. The sensitivity of the analysis is enhanced by applying a selection on the scattering angle $\ensuremath{\vartheta}$ in the ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ center-of-mass frame. We analyze events in which both $\ensuremath{\tau}$ leptons decay to hadrons, using a combination of decay channels ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$, ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\nu}}_{\ensuremath{\tau}}$, and ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$. The spin orientation of the $\ensuremath{\tau}$ leptons in these decays is reconstructed using the polarimeter-vector method. Assuming a dataset of 200 million ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ events and accounting for experimental resolutions, we expect the observation of quantum entanglement and Bell inequality violation by the Belle-II experiment will be possible with a significance well in excess of five standard deviations.

The CMS Collaboration has recently commissioned a new compact data format, named NANOAOD, reducing the per-event storage space requirement to about 1-2 kB. This represents a factor 20 reduction in storage space compared to the MINIAOD data format used previously for physics analysis at CMS. We envisage that the information stored in the NANOAOD data format is sufficient to support the majority of CMS physics analyses. NANOAOD also facilitates the dissemination of analysis methods and the automation of standard workflows for deriving conditions and object calibrations. The latest developments of this project will be presented.

Abstract Monte Carlo (MC) simulations are extensively used for various purposes in modern high-energy physics (HEP) experiments. Precision measurements of established Standard Model processes or searches for new physics often require the collection of vast amounts of data. It is often difficult to produce MC samples containing an adequate number of events to allow for a meaningful comparison with the data, as substantial computing resources are required to produce and store such samples. One solution often employed when producing MC samples for HEP experiments is to partition the phase space of particle interactions into multiple regions and produce the MC samples separately for each region. This approach allows to adapt the size of the MC samples to the needs of physics analyses that are performed in these regions. In this paper we present a procedure for combining MC samples that overlap in phase space. The procedure is based on applying suitably chosen weights to the simulated events. We refer to the procedure as “stitching”. The paper includes different examples for applying the procedure to simulated proton-proton collisions at the CERN Large Hadron Collider.

We present a feasibility study to probe quantum entanglement and Belle inequality violation in the process $\textrm{e}^{+}\textrm{e}^{-} \rightarrow \tau^{+}\tau^{-}$ at a center-of-mass energy of $\sqrt{s} = 10.579$ GeV. The sensitivity of the analysis is enhanced by applying a selection on the scattering angle $\vartheta$ in the $\tau^{+}\tau^{-}$ center-of-mass frame. We analyze events in which both $\tau$ leptons decay to hadrons, using a combination of decay channels $\tau^{-} \rightarrow \pi^{-}\nu_{\tau}$, $\tau^{-} \rightarrow \pi^{-}\pi^{0}\nu_{\tau}$, and $\tau^{-} \rightarrow \pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$. The spin orientation of the $\tau$ leptons in these decays is reconstructed using the polarimeter-vector method. Assuming a dataset of $200$ million $\tau^{+}\tau^{-}$ events and accounting for experimental resolutions, we expect the observation of quantum entanglement and Bell inequality violation by the Belle-II experiment will be possible with a significance well in excess of five standard deviations.

We apply the matrix element method (MEM) to the search for non-resonant Higgs boson pair (HH) production in the channel HH → bb̄WW* at the LHC and study the separation between the HH signal and the large irreducible background, which arises from the production of top quark pairs (tt̄). Our study focuses on events containing two leptons (electrons or muons) in the final state. The separation between signal and background is studied for experimental conditions characteristic for the ATLAS and CMS experiments during LHC Run 2, using the DELPHES fast-simulation package. We find that the tt̄ background can be reduced to a level of 0.26% for a signal efficiency of 35%.

Various theories beyond the Standard Model predict the existence of heavy resonances decaying to Higgs (H) boson pairs. In order to maximize the sensitivity of searches for such resonances, it is important that experimental analyses cover a variety of decay modes. The decay of H boson pairs to four $\tau$ leptons (HH$ \to \tau\tau\tau\tau$) has not been discussed in the literature so far. This decay mode provides a small branching fraction, but also comparatively low backgrounds. We present an algorithm for the reconstruction of the mass of the H boson pair in events in which the H boson pair decays via HH$ \to \tau\tau\tau\tau$ and the $\tau$ leptons subsequently decay into electrons, muons, or hadrons. The algorithm achieves a resolution of $7$-$22\%$ relative to the mass of the H boson pair, depending on the mass of the resonance.

Various theories beyond the Standard Model predict the existence of heavy resonances decaying to Higgs (H) boson pairs. In order to maximize the sensitivity of searches for such resonances, it is important that experimental analyses cover a variety of decay modes. The decay of H boson pairs to four $τ$ leptons (HH$ \to ττττ$) has not been discussed in the literature so far. This decay mode provides a small branching fraction, but also comparatively low backgrounds. We present an algorithm for the reconstruction of the mass of the H boson pair in events in which the H boson pair decays via HH$ \to ττττ$ and the $τ$ leptons subsequently decay into electrons, muons, or hadrons. The algorithm achieves a resolution of $7$-$22\%$ relative to the mass of the H boson pair, depending on the mass of the resonance.

We apply the matrix element method (MEM) to the search for non-resonant Higgs boson pair ($\textrm{HH}$) production in the channel $\textrm{HH} \to \textrm{b}\bar{\textrm{b}}\textrm{W}\textrm{W}^{*}$ at the LHC and study the separation between the $\textrm{HH}$ signal and the large irreducible background, which arises from the production of top quark pairs ($\textrm{t}\bar{\textrm{t}}$). Our study focuses on events containing two leptons (electrons or muons) in the final state. We find that our work has the potential to reduce the $\textrm{t}\bar{\textrm{t}}$ background by three orders of magnitude for a signal efficiency of $35\%$.