The challenge of studying perovskite solar cells’ stability with machine learning

Perovskite solar cells are the most dynamic emerging photovoltaic technology and attracts the attention of thousands of researchers worldwide. Recently, many of them are targeting device stability issues–the key challenge for this technology–which has resulted in the accumulation of a significant amount of data. The best example is the “Perovskite Database Project,” which also includes stability-related metrics. From this database, we use data on 1,800 perovskite solar cells where device stability is reported and use Random Forest to identify and study the most important factors for cell stability. By applying the concept of learning curves, we find that the potential for improving the models’ performance by adding more data of the same quality is limited. However, a significant improvement can be made by increasing data quality by reporting more complete information on the performed experiments. Furthermore, we study an in-house database with data on more than 1,000 solar cells, where the entire aging curve for each cell is available as opposed to stability metrics based on a single number. We show that the interpretation of aging experiments can strongly depend on the chosen stability metric, unnaturally favoring some cells over others. Therefore, choosing universal stability metrics is a critical question for future databases targeting this promising technology

Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a $Z$ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb$^{-1}$. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

Study of the B−→Λc+Λˉc−K−B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

The decay $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 $\mathrm{fb}^{-1}$ collected by the LHCb experiment. In the $\Lambda_{c}^+ K^{-}$ system, the $\Xi_{c}(2930)^{0}$ state observed at the BaBar and Belle experiments is resolved into two narrower states, $\Xi_{c}(2923)^{0}$ and $\Xi_{c}(2939)^{0}$, whose masses and widths are measured to be $$m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV},$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $\Lambda_{c}^{+} K^{-}$ sample. Evidence of a new $\Xi_{c}(2880)^{0}$ state is found with a local significance of $3.8\,\sigma$, whose mass and width are measured to be $2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV}$ and $12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode $\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-}$ is found with a significance of $3.7\,\sigma$. The relative branching fraction of $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ with respect to the $B^{-} \to D^{+} D^{-} K^{-}$ decay is measured to be $2.36 \pm 0.11 \pm 0.22 \pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

Measurement of the ratios of branching fractions R(D∗)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu})$ are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb${ }^{-1}$ of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}$. The measured values are $\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024$ and $\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066$, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $\rho=-0.43$. Results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages

In the shadow of extraversion : - A qualitative study of introverted individuals' experience of the Covid-19 pandemic and a norm of extraversion.

Syftet med denna sociologiska undersökning var att studera hur introverta individer har upplevt sin tillvaro innan och under Covid-19 pandemin i relation till en norm om extraversion. Studien har fokuserat på följande frågeställningar: Hur upplever introverta individer normen om extraversion? Hur upplever introverta individer att deras tillvaro har förändrats av Covid-19 pandemins utveckling? Hur upplever introverta individer att normen om extraversion har förändrats av Covid-19 pandemin? Ambitionen var att belysa problematiken med en extravert samhällsnorm vilket har genomförts utefter en hermeneutisk vetenskapsteoretisk ansats. Empiriinsamlingen baserades på åtta semi-strukturerade intervjuer med individer som identifierade sig som introverta. Studiens teoretiska ramverk bestod av Erving Goffmans (2014) dramaturgiska teori och Thomas J. Scheffs (1990) teori om sociala band vilka låg till grund för analysen av empirin.    Resultaten av studien påvisade att en norm om extraversion finns och påverkar introverta individers tillvaro negativt. Vidare kom studien fram till att introverta individer haft en övergripande positiv tillvaro under Covid-19 pandemin. Avslutningsvis visade studien på att normen om extraversion kvarstod efter det att Covid-19 pandemins restriktioner släppt. Detta innebar att en slutsats kunde dras om att normer har en stark inverkan på vårt samhälle och att förändring av dessa kan ta tid.The aim of this study in sociology was to examine how introverted individuals have experienced their being before and during the Covid-19 pandemic in relation to a norm of extraversion. The study focused on the following questions: How do introverted individuals experience the norm of extraversion? How do introverted individuals experience that their being have been changed during the Covid-19 pandemic? How do introverted individuals experience that the norm of extraversion have changed due to the Covid-19 pandemic? The ambition was to illuminate the issue of an extraverted social norm, which have been done through a hermeneutic theoretical approach. The empirical collection are based on eight semi-structured interviews of individuals who identify themselves as introverts. The theoretical framework includes Erving Goffman´s (2014) dramaturgical theory and Thomas J. Scheff´s (1990) theory of social bonds.   The result indicated that a norm of extraversion exists and affects introverted individuals negatively. The study also shows that introverted individuals had an overall positive being during the Covid-19 pandemic. Finally, a conclusion was made that norms have a strong impact on our society and that changing them takes time, which refers to the experience that the extraverted norm remains after the Covid-19 pandemic restrictions have been lifted

In the shadow of extraversion : - A qualitative study of introverted individuals' experience of the Covid-19 pandemic and a norm of extraversion.

Syftet med denna sociologiska undersökning var att studera hur introverta individer har upplevt sin tillvaro innan och under Covid-19 pandemin i relation till en norm om extraversion. Studien har fokuserat på följande frågeställningar: Hur upplever introverta individer normen om extraversion? Hur upplever introverta individer att deras tillvaro har förändrats av Covid-19 pandemins utveckling? Hur upplever introverta individer att normen om extraversion har förändrats av Covid-19 pandemin? Ambitionen var att belysa problematiken med en extravert samhällsnorm vilket har genomförts utefter en hermeneutisk vetenskapsteoretisk ansats. Empiriinsamlingen baserades på åtta semi-strukturerade intervjuer med individer som identifierade sig som introverta. Studiens teoretiska ramverk bestod av Erving Goffmans (2014) dramaturgiska teori och Thomas J. Scheffs (1990) teori om sociala band vilka låg till grund för analysen av empirin.    Resultaten av studien påvisade att en norm om extraversion finns och påverkar introverta individers tillvaro negativt. Vidare kom studien fram till att introverta individer haft en övergripande positiv tillvaro under Covid-19 pandemin. Avslutningsvis visade studien på att normen om extraversion kvarstod efter det att Covid-19 pandemins restriktioner släppt. Detta innebar att en slutsats kunde dras om att normer har en stark inverkan på vårt samhälle och att förändring av dessa kan ta tid.The aim of this study in sociology was to examine how introverted individuals have experienced their being before and during the Covid-19 pandemic in relation to a norm of extraversion. The study focused on the following questions: How do introverted individuals experience the norm of extraversion? How do introverted individuals experience that their being have been changed during the Covid-19 pandemic? How do introverted individuals experience that the norm of extraversion have changed due to the Covid-19 pandemic? The ambition was to illuminate the issue of an extraverted social norm, which have been done through a hermeneutic theoretical approach. The empirical collection are based on eight semi-structured interviews of individuals who identify themselves as introverts. The theoretical framework includes Erving Goffman´s (2014) dramaturgical theory and Thomas J. Scheff´s (1990) theory of social bonds.   The result indicated that a norm of extraversion exists and affects introverted individuals negatively. The study also shows that introverted individuals had an overall positive being during the Covid-19 pandemic. Finally, a conclusion was made that norms have a strong impact on our society and that changing them takes time, which refers to the experience that the extraverted norm remains after the Covid-19 pandemic restrictions have been lifted

Study of the doubly charmed tetraquark Tcc+T_{cc}^+

An exotic narrow state in the $D^0D^0\pi^+$ mass spectrum just below the $D^{*+}D^0$ mass threshold is studied using a data set corresponding to an integrated luminosity of 9 fb$^{-1}$ acquired with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The state is consistent with the ground isoscalar $T^+_{cc}$ tetraquark with a quark content of $cc\bar{u}\bar{d}$ and spin-parity quantum numbers $\mathrm{J}^{\mathrm{P}}=1^+$. Study of the $DD$ mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell $D^{*+}$ mesons is confirmed by the $D^0\pi^+$ mass distribution. The mass of the resonance and its coupling to the $D^{*}D$ system are analysed. Resonance parameters including the pole position, scattering length, effective range and compositeness are measured to reveal important information about the nature of the $T^+_{cc}$ state. In addition, an unexpected dependence of the production rate on track multiplicity is observed

Measurement of the lifetimes of promptly produced Ωc0 and Ξc0 baryons

International audienceA measurement of the lifetimes of the Ωc0 and Ξc0 baryons is reported using proton–proton collision data at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.4fb-1 collected by the LHCb experiment. The Ωc0 and Ξc0 baryons are produced directly from proton interactions and reconstructed in the pK-K-π+ final state. The Ωc0 lifetime is measured to be 276.5±13.4±4.4±0.7fs, and the Ξc0 lifetime is measured to be 148.0±2.3±2.2±0.2fs, where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the D0 lifetime. These results confirm previous LHCb measurements based on semileptonic beauty-hadron decays, which disagree with earlier results of a four times shorter Ωc0 lifetime, and provide the single most precise measurement of the Ωc0 lifetime

Observation of the suppressed Λb0→DpK- decay with D→K+π- and measurement of its CP asymmetry

International audienceA study of Λb0 baryon decays to the DpK- final state is presented based on a proton-proton collision data sample corresponding to an integrated luminosity of 9  fb-1 collected with the LHCb detector. Two Λb0 decays are considered, Λb0→DpK- with D→K-π+ and D→K+π-, where D represents a superposition of D0 and D¯0 states. The latter process is expected to be suppressed relative to the former, and is observed for the first time. The ratio of branching fractions of the two decays is measured, and the CP asymmetry of the suppressed mode, which is sensitive to the Cabibbo-Kobayashi-Maskawa angle γ, is also reported

Nuclear modification factor of neutral pions in the forward and backward regions in ppPb collisions

The nuclear modification factor of neutral pions is measured in proton-lead collisions collected at a center-of-mass energy per nucleon of $8.16$ TeV with the LHCb detector. The $\pi^0$ production cross section is measured differentially in transverse momentum ($p_{T}$) for 1.5π0 production cross section is measured differentially in transverse momentum (pT) for 1.5<pT<10.0  GeV and in center-of-mass pseudorapidity (ηc.m.) regions 2.5<ηc.m.<3.5 (forward) and -4.0<ηc.m.<-3.0 (backward) defined relative to the proton beam direction. The forward measurement shows a sizable suppression of π0 production, while the backward measurement shows the first evidence of π0 enhancement in proton-lead collisions at the LHC. Together, these measurements provide precise constraints on models of nuclear structure and particle production in high-energy nuclear collisions.The nuclear modification factor of neutral pions is measured in proton-lead collisions collected at a center-of-mass energy per nucleon of 8.16~{\rm TeV}$with the LHCb detector. The$\pi^0$production cross section is measured differentially in transverse momentum ($p_{\rm T}$) for$1.5<p_{\rm T}<10.0~{\rm GeV}$and in center-of-mass pseudorapidity ($\eta_{\rm c.m.}$) regions$2.5<\eta_{\rm c.m.}<3.5$(forward) and$-4.0<\eta_{\rm c.m.}<-3.0$(backward) defined relative to the proton beam direction. The forward measurement shows a sizable suppression of$\pi^0$production, while the backward measurement shows the first evidence of$\pi^0$ enhancement in proton-lead collisions at the LHC. Together, these measurements provide precise constraints on models of nuclear structure and particle production in high-energy nuclear collisions