Hunting for neutral, long-lived exotica at the LHC using a missing transverse energy signature

Searches at the Large Hadron Collider (LHC) for neutral, long-lived particles have historically relied on the detection of displaced particles produced by their decay $\textit{within}$ the detector volume. In this paper we study the potential of the complementary signature comprising of the missing transverse energy ($E_T^{miss}$) signal, traditionally used to look for dark matter, e.g., the lightest supersymmetric particle (LSP), to extend the LHC coverage to models with long-lived (LL) particles when they decay $\textit{outside}$ the detector. Using CMS and ATLAS analyses at the 8 TeV LHC, we set an upper limit at the 95% confidence level (CL) on the production cross sections for two specific scenarios: (i) a model with a heavy non-standard model Higgs boson decaying to a LL scalar and (ii) an R-parity violating RPV SUSY model with a LL neutralino. We show that this method can significantly extend the LHC sensitivity to neutral, LL particles with arbitrary large lifetimes and that the limits obtained from a $E_T^{miss}$ signal are comparable to those from displaced particle searches for decay distances above a few meters. Results obtained in this study do not not depend on the specific decay channel of the LL particle and therefore are model-independent in this sense. We provide limits for the whole two-dimensional plane in terms of the mass of the LL particle and the mass of the mediator up to masses of 2 TeV including particular benchmarks studied in the original experimental papers. We have made these limits available in the form of a grid which can be used for the interpretation of various other new physics models.Comment: 28 page

Analytic approximations to the phase diagram of the Jaynes-Cummings-Hubbard model with application to ion chains

We discuss analytic approximations to the ground state phase diagram of the homogeneous Jaynes-Cummings-Hubbard (JCH) Hamiltonian with general short-range hopping. The JCH model describes e.g. radial phonon excitations of a linear chain of ions coupled to an external laser field tuned to the red motional sideband with Coulomb mediated hopping or an array of high-$Q$ coupled cavities containing a two-level atom and photons. Specifically we consider the cases of a linear array of coupled cavities and a linear ion chain. We derive approximate analytic expressions for the boundaries between Mott-insulating and superfluid phases and give explicit expressions for the critical value of the hopping amplitude within the different approximation schemes. In the case of an array of cavities, which is represented by the standard JCH model we compare both approximations to numerical data from density-matrix renormalization group (DMRG) calculations.Comment: 9 pages, 5 figures, extended and corrected second versio

Infinite-dimensional port-Hamiltonian systems with a stationary interface

We consider two systems of two conservation laws that are defined on complementary spatial intervals and coupled by an interface as a single port-Hamiltonian system. In case of a fixed interface position, we characterize the boundary and interface conditions for which the associated port-Hamiltonian operator generates a contraction semigroup. Furthermore, we present sufficient conditions for the exponential stability of the generated $C_0$-semigroup. The results are illustrated by the example of two acoustic waveguides coupled by an interface consisting of some membrane.Comment: arXiv admin note: text overlap with arXiv:2301.0734

Bargain Hunting on Black Friday - Making Great Deals and Bragging About Them

Online customer reviews (OCRs) are helpful when they provide an unbiased view on a product. Large-scale shopping events (e.g., Black Friday) generate large volumes of OCRs. We hypothesize that OCRs from such events are biased due to price discounts and smart shopper feelings. To test our hypotheses, we use OCR data of a large US electronics retailer that emerge from Black Friday purchases and regular purchases. We find that numerical ratings from Black Friday purchases are considerably higher. This effect is also observable in an increase of the average numerical rating through Black Friday purchases. We further observe that textual OCR content from Black Friday purchases focuses more on the purchase conditions (e.g., price discounts) at the expense of other, potentially more helpful content. We further provide managerial implications on how retailers may counteract the negative consequences of such biased OCRs on the quality of their OCR systems

Scorzonera sensu lato (Asteraceae, Cichorieae) – taxonomic reassessment in the light of new molecular phylogenetic and carpological analyses

Scorzonera comprises 180–190 species and belongs to the subtribe Scorzonerinae. Its circumscription has long been the subject of debate and available molecular phylogenetic analyses affirmed the polyphyly of Scorzonera in its wide sense. We provide a re-evaluation of Scorzonera and other related genera, based on carpological (including anatomical) and extended molecular phylogenetic analyses. We present, for the first time, a comprehensive sampling, including Scorzonera in its widest sense and all other genera recognised in the Scorzonerinae. We conducted phylogenetic analyses using Maximum Parsimony, Maximum Likelihood and Bayesian analyses, based on sequences of the nuclear ribosomal ITS and of two plastid markers (partial rbcL and matK) and Maximum Parsimony for reconstructing the carpological character states at ancestral nodes. Achene characters, especially related to pericarp anatomy, such as general topography of the tissue types, disposition of the mechanical tissue and direction of its fibres, presence or absence of air cavities, provide, in certain cases, support for the phylogenetic lineages revealed. Confirming the polyphyly of Scorzonera, we propose a revised classification of the subtribe, accepting the genera Scorzonera (including four major clades: Scorzonera s. str., S. purpurea, S. albicaulis and Podospermum), Gelasia, Lipschitzia gen. nov. (for the Scorzonera divaricata clade), Pseudopodospermum, Pterachaenia (also including Scorzonera codringtonii), Ramaliella gen. nov. (for the S. polyclada clade) and Takhtajaniantha. A key to the revised genera and a characterisation of the genera and major clades are provided

Tell Me Why (I Want It That Way) – Effects of Explanations and Online Customer Reviews on Trust in Recommender Systems

Review-based recommender systems (RS) have shown great potential in helping users manage information overload and find suitable items. However, a lack of trust still impedes the widespread acceptance of RS. To increase users’ trust, research proposes various methods to generate justifications or explanations. Furthermore, online customer reviews (OCRs) are found to be a trustworthy and reliable source of information. However, it is still unclear how justifications compare to explanations in their influence on users’ trust and whether basing them on OCRs additionally adds trust. Hence, we conduct an online experiment with 531 participants and find that explanations exceed justifications in increasing users’ trust, while basing them on OCRs directly increases users’ intentions to use the system and adopt recommendations without increasing trust in the RS themselves. Unifying different research streams from review-based RS and Explainable Artificial Intelligence, we provide an overarching, holistic view on the conception of justifications and explanations

Persistence problems for fractional processes

In this thesis, we deal with several persistence problems for fractional processes. Persistence concerns the event that a stochastic process has a long excursion staying below or above a certain barrier. A central question in this context is the analysis of the probability of this event - the so-called persistence probability. We first consider the persistence probabilities of integrated fractional Brownian motion and fractionally integrated Brownian motion. While it is well-known that these persistence probabilities decay asymptotically polynomially, their polynomial rates are unknown except for the special cases of Brownian motion and integrated Brownian motion. We show that for both processes, the polynomial rate is a continuous function in the Hurst parameter and determine its asymptotic behaviour at the boundaries of the respective parameter domain. Subsequently, we study persistence probabilities of mixed processes, such as mixed fractional Brownian motion. Precisely, we consider the sum of two self-similar centred Gaussian processes with different self-similarity indices and show that, under non-negativity assumptions of covariance functions and some further minor conditions, the persistence probability of the sum decays asymptotically polynomially with the same polynomial rate as for the single process with the greater self-similarity index. In particular, this determines the polynomial rate of the persistence probability of mixed fractional Brownian motion. Lastly, we give estimates for the persistence probabilities of further fractional processes of interest, namely the bifractional Brownian motion and the fractional Ornstein-Uhlenbeck process

Dynamic Pricing on Two-Sided Platforms: Consequences on Customers’ Fairness Perceptions and Purchase Intentions

Technological advancements simplify the application of dynamic pricing, i.e., the flexible and rapid adjustment of prices to changes in demand. Consequently, companies increasingly use dynamic pricing in their business models, although research reports negative consequences on customer fairness perceptions. This holds not only for one-sided businesses, but also for popular two-sided platforms. However, these platforms differ from one-sided businesses in that the total prices paid by customers consist of product prices and platform fees – and both price components can be dynamically adjusted. In an online experiment, we examine customers’ fairness perceptions and purchase intentions when product price and platform fee change dynamically. We find that dynamic price increases reduce fairness perceptions and purchase intentions, while the cause of the price increases is irrelevant to customers. These results indicate an imbalance in the risks and benefits of dynamic pricing between the pricing strategies of the platform and the provider

Lead-free, luminescent perovskite nanocrystals obtained through ambient condition synthesis

Heterovalent substitution of toxic lead is an increasingly popular design strategy to obtain environmentally sustainable variants of the exciting material class of halide perovskites. Perovskite nanocrystals (NCs) obtained through solution-based methods exhibit exceedingly high optical quality. Unfortunately, most of these synthesis routes still require reaction under inert gas and at very high temperatures. Herein we present a novel synthesis routine for lead-free double perovskite NCs. We combine hot injection and ligand-assisted reprecipitation (LARP) methods to achieve a low-temperature and ambient atmosphere-based synthesis for manganese-doped Cs_{2}NaBiCl_{6} NCs. Mn incorporation is critical for the otherwise non-emissive material, with a 9:1 Bi:Mn precursor ratio maximizing the bright orange photoluminescence (PL) and quantum yield (QY). Higher temperatures slightly increased the material's performance, yet NCs synthesized at room temperature were still emissive, highlighting the versatility of the synthetic approach. Furthermore, the NCs show excellent long-term stability in ambient conditions, facilitating additional investigations and energy-related applications

Precision tools and models to narrow in on the 750 GeV diphoton resonance

The hints for a new resonance at 750 GeV from ATLAS and CMS have triggered a significant amount of attention. Since the simplest extensions of the standard model cannot accommodate the observation, many alternatives have been considered to explain the excess. Here we focus on several proposed renormalisable weakly-coupled models and revisit results given in the literature. We point out that physically important subtleties are often missed or neglected. To facilitate the study of the excess we have created a collection of 40 model files, selected from recent literature, for the Mathematica package SARAH. With SARAH one can generate files to perform numerical studies using the tailor-made spectrum generators FlexibleSUSY and SPheno. These have been extended to automatically include crucial higher order corrections to the diphoton and digluon decay rates for both CP-even and CP-odd scalars. Additionally, we have extended the UFO and CalcHep interfaces of SARAH, to pass the precise information about the effective vertices from the spectrum generator to a Monte-Carlo tool. Finally, as an example to demonstrate the power of the entire setup, we present a new supersymmetric model that accommodates the diphoton excess, explicitly demonstrating how a large width can be obtained. We explicitly show several steps in detail to elucidate the use of these public tools in the precision study of this model.Comment: 184 pages, 24 figures; model files available at http://sarah.hepforge.org/Diphoton_Models.tar.gz; v2: added a few clarifications and reference