Measurement of top quark polarisation in t-channel single top quark production

A first measurement of the top quark spin asymmetry, sensitive to the top quark polarisation, in $t$-channel single top quark production is presented. It is based on a sample of pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 $\mathrm{fb^{-1}}$. A high-purity sample of $t$-channel single top quark events with an isolated muon is selected. Signal and background components are estimated using a fit to data. A differential cross section measurement, corrected for detector effects, of an angular observable sensitive to the top quark polarisation is performed. The differential distribution is used to extract a top quark spin asymmetry of $0.26 \pm 0.03 \textrm{(stat)} \pm 0.10 \textrm{(syst)}$, which is compatible with a p-value of $4.6\%$ with the standard model prediction of 0.44.Comment: presented at 9th International Workshop on Top Quark Physics Olomouc, Czech Republic, September 19–23, 201

Üksiku t-kvargi omaduste mõõtmine CMS-detektoris

Pärast hiljutist Higgsi bosoni avastamist on leitud kõik osakestefüüsika standardmudeli (SM) poolt ennustatud osakesed. Ometi on põhjust arvata, et tegu pole lõpliku teooriaga, kuna mitmed nähtused, nagu tumeaine või neutriinode massid ei ole SM-ga seletatavad. Üks huvitav uurimisobjekt, mille täpsete mõõtmiste abil saab kindlaks teha võimalikke kõrvalekaldeid SM ennustustest, on t-kvark. T-kvark on raskeim avastatud elementaarosake ja laguneb seetõttu erinevalt teistest kvarkidest enne liitosakeste hadronite moodustamist, võimaldades erandlikult uurida paljast kvarki. Oma massi tõttu on t-kvark ka osake, mis omab kõige tugevamat vastasmõju Higgsi bosoniga. T-kvargid saavad tekkida kas kvargi- ja antikvargi paaridena tugeva vastastikmõju abil või väiksemal määral üksikute (anti)kvarkidena nõrga vastastikmõju kaudu. Seda tõenäosust, et vastav protsess aset leiab, iseloomustab tekkeristlõige, mis on kõigi osakestefüüsika protsesside oluliseks omaduseks. Üksikute t-kvarkide teket vaadeldi esmakordselt alles 2009. aastal, samas on nende abil võimalik uurida mitmeid t-kvarkide omadusi paremini kui t-kvargi paaride abil. Näiteks ei jõua t-kvargi spinn enne lagunemist muutuda ja seetõttu saab seda üksiku t-kvargi laguproduktide kaudu mõõta, kusjuures SM ennustab, et kõik tekkinud üksikud t-kvargid peaksid olema vasakukäelised. Suur Hadronite Põrguti (LHC) on 27 km pikkune maailma suurim ja kõrgeima energiaga osakeste kiirendi, kus põrgatatakse vastassuundades liikuvaid prootonite kimpe masskeskme energiatel kuni 14 TeV. LHC-s tegutseb seitse eksperimenti, antud töö kasutab üldotstarbelise detektori CMS-iga tehtud mõõtmisi. Doktoritöös on mõõdetud üksiku t-kvargi ristlõiked prootonite põrgetel masskeskme energiatel 7 TeV ja 8 TeV ning üksiku t-kvargi polarisatsioon energial 8 TeV.After the recent discovery of the Higgs boson, all particles predicted by the standard model of particle physics (SM) have been found. However, since many phenomena, such as dark matter or neutrino masses, are not explained by SM, there is reason to believe that it is not the final theory. A particularly interesting object of study to check for possible deviations from SM predictions is the top quark. Top quark is the heaviest discovered particle. Its very high mass causes the top quark to decay before forming hadrons in contrast to other quarks, which always form composite particles. Thus, the top quark gives us a special opportunity to study a bare quark. Due to its mass, the top quark is also the particle with the strongest interaction with the Higgs boson. Top quarks are created either in quark-antiquark pairs through the strong interaction or less frequently as single top (anti)quarks through weak interaction. The probability of being created is measured by production cross section, which is an important property of all particle physics processes. Despite the smaller production cross section, single top production offers possibilities to study some of the top quark properties in a better way compared to pair production. For example, all single top quarks are created left-handed according to SM prediction, and as the top quark decays before the spin has time to change, the spin of the top quark can be measured through the decay products. Single top quark production was first observed only recently, in 2009. The Large Hadron Collider (LHC) is the world’s biggest and highest energy particle collider with a circumference of 27 km, colliding beams of protons circulating in opposite directions at centre-of-mass energies up to 14 TeV. There are seven experiments in operation at the LHC, this work utilises the data collected with the general purpose detector Compact Muon Solenoid (CMS). In this thesis, the measurement of single top quark cross section is performed at proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV, and single top quark polarisation is measured at 8 TeV

Measurement of the t(t)over-bar production cross section in the dilepton channel in pp collisions at √s=8 TeV

The top-antitop quark (t (t) over bar) production cross section is measured in proton-proton collisions at root s = 8 TeV with the CMS experiment at the LHC, using a data sample corresponding to an integrated luminosity of 5.3 fb(-1). The measurement is performed by analysing events with a pair of electrons or muons, or one electron and one muon, and at least two jets, one of which is identified as originating from hadronisation of a bottom quark. The measured cross section is 239 +/- 2 (stat.) +/- 11 (syst.) +/- 6 (lum.) pb, for an assumed top-quark mass of 172.5 GeV, in agreement with the prediction of the standard model

Search for pair-produced resonances decaying to jet pairs in proton-proton collisions at √s=8 TeV

Results are reported of a general search for pair production of heavy resonances decaying to pairs of hadronic jets in events with at least four jets. The study is based on up to 19.4 fb(-1) of integrated luminosity from proton-proton collisions at a center-of-mass energy of 8 TeV, recorded with the CMS detector at the LHC. Limits are determined on the production of scalar top quarks (top squarks) in the framework of R-parity violating supersymmetry and on the production of color-octet vector bosons (colorons). First limits at the LHC are placed on top squark production for two scenarios. The first assumes decay to a bottom quark and a light-flavor quark and is excluded for masses between 200 and 385 GeV, and the second assumes decay to a pair of light-flavor quarks and is excluded for masses between 200 and 350 GeV at 95% confidence level. Previous limits on colorons decaying to light-flavor quarks are extended to exclude masses from 200 to 835 GeV

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Search for light bosons in decays of the 125 GeV Higgs boson in proton-proton collisions at root s=8 TeV

Peer reviewe

Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon

The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe

Severe early onset preeclampsia: short and long term clinical, psychosocial and biochemical aspects

Preeclampsia is a pregnancy specific disorder commonly defined as de novo hypertension and proteinuria after 20 weeks gestational age. It occurs in approximately 3-5% of pregnancies and it is still a major cause of both foetal and maternal morbidity and mortality worldwide1. As extensive research has not yet elucidated the aetiology of preeclampsia, there are no rational preventive or therapeutic interventions available. The only rational treatment is delivery, which benefits the mother but is not in the interest of the foetus, if remote from term. Early onset preeclampsia (<32 weeks’ gestational age) occurs in less than 1% of pregnancies. It is, however often associated with maternal morbidity as the risk of progression to severe maternal disease is inversely related with gestational age at onset2. Resulting prematurity is therefore the main cause of neonatal mortality and morbidity in patients with severe preeclampsia3. Although the discussion is ongoing, perinatal survival is suggested to be increased in patients with preterm preeclampsia by expectant, non-interventional management. This temporising treatment option to lengthen pregnancy includes the use of antihypertensive medication to control hypertension, magnesium sulphate to prevent eclampsia and corticosteroids to enhance foetal lung maturity4. With optimal maternal haemodynamic status and reassuring foetal condition this results on average in an extension of 2 weeks. Prolongation of these pregnancies is a great challenge for clinicians to balance between potential maternal risks on one the eve hand and possible foetal benefits on the other. Clinical controversies regarding prolongation of preterm preeclamptic pregnancies still exist – also taking into account that preeclampsia is the leading cause of maternal mortality in the Netherlands5 - a debate which is even more pronounced in very preterm pregnancies with questionable foetal viability6-9. Do maternal risks of prolongation of these very early pregnancies outweigh the chances of neonatal survival? Counselling of women with very early onset preeclampsia not only comprises of knowledge of the outcome of those particular pregnancies, but also knowledge of outcomes of future pregnancies of these women is of major clinical importance. This thesis opens with a review of the literature on identifiable risk factors of preeclampsia

Search for Higgsino pair production in pp collisions at root s=13 TeV in final states with large missing transverse momentum and two Higgs bosons decaying via H -> b(b)over bar

Results are reported from a search for new physics in 13 TeV proton-proton collisions in the final state with large missing transverse momentum and two Higgs bosons decaying via H -> b(b)over bar. The search uses a data sample accumulated by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb(-1). The search is motivated by models based on gauge-mediated supersymmetry breaking, which predict the electroweak production of a pair of Higgsinos, each of which can decay via a cascade process to a Higgs boson and an undetected lightest supersymmetric particle. The observed event yields in the signal regions are consistent with the standard model background expectation obtained from control regions in data. Higgsinos in the mass range 230-770 GeV are excluded at 95% confidence level in the context of a simplified model for the production and decay of approximately degenerate Higgsinos.Peer reviewe