Searching for degenerate Higgs bosons using a profile likelihood ratio method

ATLAS and CMS collaborations at the Large Hadron Collider have observed a new resonance consistent with the standard model Higgs boson. However, it has been suggested that the observed signal could also be produced by multiple nearly mass-degenerate states that couple differently to the standard model particles. In this work, a method to discriminate between the hypothesis of a single Higgs boson and that of multiple mass-degenerate Higgs bosons was developed. Using the matrix of measured signal strengths in different production and decay modes, parametrizations for the two hypotheses were constructed as a general rank 1 matrix and the most general 5 x 4 matrix, respectively. The test statistic was defined as a ratio of profile likelihoods for the two hypotheses. The method was applied to the CMS measurements. The expected test statistic distribution was estimated twice by generating pseudo-experiments according to both the standard model hypothesis and the single Higgs boson hypothesis best fitting the data. The p-value for the single Higgs boson hypothesis was defined from both expected test statistic distributions, and it was (8.0 ± 0.3)% and (11.0±0.3)%, respectively. In addition to this, a p-value was also estimated in an alternative way using a χ2 distribution, fitted to the pseudo-experiments for the standard model Higgs boson hypothesis. The resulting p-value was 10.8%. Thus the three estimates yield similar p-values for the single Higgs boson hypothesis. These results suggest that the CMS data is compatible with the single Higgs boson hypothesis, as in the standard model. Furthermore, the result is insensitive to choice of the single Higgs boson hypothesis used to derive it, and it does not depend on the precise shape of the test statistic distribution. The developed method can be applied also to other arbitrarily-sized matrices, and it takes into account the uncertainties on the measurements, missing elements of data, and possible correlations. This thesis is an extensive description of the method that has also been published in EPJC (David, Heikkilä and Petrucciani), and the method has been used in the final Run 1 Higgs combination and properties article (CMS Collaboration, incl. Heikkilä).Suuren hadronitörmäyttimen kaksi koetta, ATLAS ja CMS, ovat havainneet uuden hiukkasen, joka on standardimallin Higgsin bosonin kaltainen. On kuitenkin ehdotettu, että havaittu signaali voisi aiheutua useasta, lähes samanmassaisista hiukkasista, jotka kytkeytyvät eri vahvuuksilla standardimallin hiukkasiin. Työssä kehitettiin menetelmä, jonka avulla voidaan tutkia kuinka hyvin hypoteesi yhdestä Higgsin bosonista sopii mittaustuloksiin verrattuna hypoteesiin samanmassaisista Higgsin bosoneista. Nollahypoteesi ja yleinen hypoteesi parametrisoitiin vastaavasti asteen 1 matriisina sekä yleisimpänä 5 x 4 matriisina. Testisuure määriteltiin osamäärätestisuureen, eli hypoteesejä vastaavien uskottavuusfunktioiden suhdeluvun, avulla. Menetelmää sovellettiin CMS-mittauksiin.Testisuureen odotettua jakaumaa arvioitiin näennäiskokeilla, jotka luotiin kahta lähtöasetelmaa - standardimallia sekä suurimman uskottavuuden estimaatteja - käyttäen. P-arvo nollahypoteesin mukaisessa tilanteessa määritettiin molemmista testisuureen odotetuista jakaumista ja saadut p-arvot olivat vastaavasti (8.0 ± 0.3)% sekä (11.0 ± 0.3)%. P-arvo määritettiin myös vaihtoehtoisella tavalla, jossa χ2 -jakauma sovitettiin siihen testisuureen odotettuun jakaumaan, joka arvioitiin standardimallin mukaisilla näennäiskokeilla. Tällöin p-arvo oli 10.8%. Tuloksena saadut kolme p-arvoa olivat näin ollen samansuuruisia. Saadut tulokset osoittavat, että CMS-mittaustulokset ovat yhteensopivia nollahypoteesin eli yhden Higgsin bosonin hypoteesin kanssa, aivan kuten standardimallissa. Huomioitakoon, että saatu p-arvo ei riipu näennäiskokeiden luomiseen valitusta lähtöasetelmasta tai testisuureen odotetun jakauman tarkasta muodosta. Työssä kehitettyä menetelmää voidaan soveltaa myös muihin mielivaltaisen kokoisiin matriiseihin, ja se huomioi mittausten virheet, puuttuvat mittaukset sekä mahdolliset korrelaatiot. Tämä työ on laajempi kuvaus menetelmästä, joka on myös julkaistu EPJC:ssä (David, Heikkilä ja Petrucciani) ja jota on käytetty CMS-kokeen lopullisessa Run 1 Higgs-kombinaatiojulkaisussa (CMS-kollaboraatio, ml. Heikkilä)

Validation of the Helsinki University Hospital prevent pressure Injury Risk Assessment Tool : a prospective observational study

Background Pressure injures are a common adverse event in a hospital, and they are one of the most important quality indicators of patient care. Risk assessment is recommended as the first step in the prevention of pressure injuries. A Prevent Pressure Injury Risk Assessment Tool is a new tool for risk assessment that was developed by the Helsinki University Hospital. Aim The aim of this study was to evaluate the predictive validity and the concurrent validity of the Prevent Pressure Injury Risk Assessment Tool in acute care. Method The prospective observational study was conducted in 19 in-patient wards representing internal medicine, neurology, and surgery during 2017-2018. The participants' inclusion criteria were: age >= 18 years old, no pressure injury on admission to the hospital and consenting to participate. The data collected by physical assessment of patients was combined with data from electronic patient records. Each patient was assessed by two different nurses with the Prevent Pressure Injury Risk Assessment Tool and the Braden Scale at patient admission. Furthermore, skin condition was observed throughout the hospital stay. Results Of the 637 patients accepted for the study, 10 (1.6%) developed a pressure injury during the hospital stay. Poisson regression analysis showed that pressure injuries were more likely in high-risk patients compared to those with low-risk. The sensitivity of the Prevent Pressure Injury Risk Assessment Tool was adequate (75%), while specificity was poor (40%). A moderate correlation was found between the Prevent Pressure Injury Risk Assessment Tool and the Braden Scale. Conclusions The Prevent Pressure Injury Risk Assessment Tool may be useful for identifying the adult pressure injury risk patients in acute care. Further research is needed to evaluate interrater reliability, and usability and validity with different patient populations.Peer reviewe

Pressure injury prevalence and incidence in acute inpatient care and related risk factors : A cross-sectional national study

Publisher Copyright: © 2021 The Authors. International Wound Journal published by Medicalhelplines.com Inc (3M) and John Wiley & Sons Ltd.The aim of this national cross-sectional study was to explore the prevalence of pressure injuries and incidence of hospital-acquired pressure injuries, and the relating factors in somatic-specialised inpatient care in Finland. The study was conducted in 16 (out of 21) Finnish health care organisations offering specialised health care services. Data were collected in 2018 and 2019 from adult patients (N = 5902) in inpatient, emergency follow-up, and rehabilitation units. Pressure injury prevalence (all stages/categories) was 12.7%, and the incidence of hospital-acquired pressure injuries was 10%. Of the participants, 2.6% had at least one pressure injury at admission. The risk of hospital-acquired pressure injuries was increased for medical patients with a higher age, the inability to move independently, mode of arrival, being underweight, and the absence of a skin assessment or pressure injury risk assessment at admission. For surgical patients, the risk was associated with the inability to move independently, mode of arrival, and lack of skin assessment at admission, while being overweight protected the patients. Overall, medical patients were in greater risk of hospital-acquired pressure injuries than the surgical patients. An assessment of the pressure injury risk and skin status should be carried out more systematically in Finnish acute care hospitals.Peer reviewe

Pressure injury prevalence and incidence in acute inpatient care and related risk factors: A cross-sectional national study

The aim of this national cross-sectional study was to explore the prevalence of pressure injuries and incidence of hospital-acquired pressure injuries, and the relating factors in somatic-specialised inpatient care in Finland. The study was conducted in 16 (out of 21) Finnish health care organisations offering specialised health care services. Data were collected in 2018 and 2019 from adult patients (N = 5902) in inpatient, emergency follow-up, and rehabilitation units. Pressure injury prevalence (all stages/categories) was 12.7%, and the incidence of hospital-acquired pressure injuries was 10%. Of the participants, 2.6% had at least one pressure injury at admission. The risk of hospital-acquired pressure injuries was increased for medical patients with a higher age, the inability to move independently, mode of arrival, being underweight, and the absence of a skin assessment or pressure injury risk assessment at admission. For surgical patients, the risk was associated with the inability to move independently, mode of arrival, and lack of skin assessment at admission, while being overweight protected the patients. Overall, medical patients were in greater risk of hospital-acquired pressure injuries than the surgical patients. An assessment of the pressure injury risk and skin status should be carried out more systematically in Finnish acute care hospitals

Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at √s = 13 TeV

Abstract The parton-level top quark (t) forward-backward asymmetry and the anomalous chromoelectric (d̂ t) and chromomagnetic (μ̂ t) moments have been measured using LHC pp collisions at a center-of-mass energy of 13 TeV, collected in the CMS detector in a data sample corresponding to an integrated luminosity of 35.9 fb−1. The linearized variable AFB(1) is used to approximate the asymmetry. Candidate t t ¯ events decaying to a muon or electron and jets in final states with low and high Lorentz boosts are selected and reconstructed using a fit of the kinematic distributions of the decay products to those expected for t t ¯ final states. The values found for the parameters are AFB(1)=0.048−0.087+0.095(stat)−0.029+0.020(syst),μ̂t=−0.024−0.009+0.013(stat)−0.011+0.016(syst), and a limit is placed on the magnitude of | d̂ t| < 0.03 at 95% confidence level. [Figure not available: see fulltext.

Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

Peer reviewe

An embedding technique to determine ττ backgrounds in proton-proton collision data

An embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1).Peer reviewe

MUSiC : a model-unspecific search for new physics in proton-proton collisions at root s=13TeV

Results of the Model Unspecific Search in CMS (MUSiC), using proton-proton collision data recorded at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.Peer reviewe

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

Measurement of prompt open-charm production cross sections in proton-proton collisions at root s=13 TeV

The production cross sections for prompt open-charm mesons in proton-proton collisions at a center-of-mass energy of 13TeV are reported. The measurement is performed using a data sample collected by the CMS experiment corresponding to an integrated luminosity of 29 nb(-1). The differential production cross sections of the D*(+/-), D-+/-, and D-0 ((D) over bar (0)) mesons are presented in ranges of transverse momentum and pseudorapidity 4 < p(T) < 100 GeV and vertical bar eta vertical bar < 2.1, respectively. The results are compared to several theoretical calculations and to previous measurements.Peer reviewe