Abstract A search for pair production of heavy scalar leptoquarks (LQs), each decaying into a top quark and a $$\tau $$ τ lepton, is presented. The search considers final states with an electron or a ...muon, one or two $$\tau $$ τ leptons that decayed to hadrons, and additional jets. The data were collected in 2016 in proton–proton collisions at $$\sqrt{s}=13\,\text {Te}\text {V} $$ s=13Te with the CMS detector at the LHC, and correspond to an integrated luminosity of 35.9$$\,\text {fb}^{-1}$$ fb-1 . No evidence for pair production of LQs is found. Assuming a branching fraction of unity for the decay $$\mathrm {LQ} \rightarrow \mathrm {t}\tau $$ LQ→tτ , upper limits on the production cross section are set as a function of LQ mass, excluding masses below 900$$\,\text {Ge}\text {V}$$ Ge at 95% confidence level. These results provide the most stringent limits to date on the production of scalar LQs that decay to a top quark and a $$\tau $$ τ lepton.
Abstract A search for physics beyond the standard model (SM) in the final state with a hadronically decaying tau lepton and a neutrino is presented. This analysis is based on data recorded by the CMS ...experiment from proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to a total integrated luminosity of 138 fb −1. The transverse mass spectrum is analyzed for the presence of new physics. No significant deviation from the SM prediction is observed. Limits are set on the production cross section of a W′ boson decaying into a tau lepton and a neutrino. Lower limits are set on the mass of the sequential SM-like heavy charged vector boson and the mass of a quantum black hole. Upper limits are placed on the couplings of a new boson to the SM fermions. Constraints are put on a nonuniversal gauge interaction model and an effective field theory model. For the first time, upper limits on the cross section of t-channel leptoquark (LQ) exchange are presented. These limits are translated into exclusion limits on the LQ mass and on its coupling in the t-channel. The sensitivity of this analysis extends into the parameter space of LQ models that attempt to explain the anomalies observed in B meson decays. The limits presented for the various interpretations are the most stringent to date. Additionally, a model-independent limit is provided.
Abstract A search for the electroweak production of a vector-like quark T′, decaying to a top quark and a Higgs boson is presented. The search is based on a sample of proton-proton collision events ...recorded at the LHC at s $$ \sqrt{s} $$ = 13 TeV, corresponding to an integrated luminosity of 138 fb −1. This is the first T′ search that exploits the Higgs boson decay to a pair of photons. For narrow isospin singlet T′ states with masses up to 1.1 TeV, the excellent diphoton invariant mass resolution of 1–2% results in an increased sensitivity compared to previous searches based on the same production mechanism. The electroweak production of a T′ quark with mass up to 960 GeV is excluded at 95% confidence level, assuming a coupling strength κ T = 0.25 and a relative decay width Γ/M T′ < 5%.
We present a detailed chemical abundance analysis of the brightest star in the ultra-faint dwarf (UFD) galaxy candidate Cetus II from high-resolution Magellan/MIKE spectra. For this star, DES ...J011740.53-173053, abundances or upper limits of 18 elements from Carbon to Europium are derived. Its chemical abundances generally follow those of other UFD galaxy stars, with a slight enhancement of the alpha-elements (Mg, Si, and Ca) and low neutron-capture element (Sr, Ba, Eu) abundances supporting the classification of Cetus II as a likely UFD. The star exhibits lower Sc, Ti, and V abundances than Milky Way (MW) halo stars with similar metallicity. This signature is consistent with yields from a supernova (SN) originating from a star with a mass of ~11.2 solar masses. In addition, the star has a Potassium abundance of K/Fe = 0.81 which is somewhat higher than the K abundances of MW halo stars with similar metallicity, a signature which is also present in a number of UFD galaxies. A comparison including globular clusters (GC) and stellar stream stars suggests that high K is a specific characteristic for some UFD galaxy stars and can thus be used to help classify objects as UFD galaxies.
Abstract A search for physics beyond the standard model in final states with at least one photon, large transverse momentum imbalance, and large total transverse event activity is presented. Such ...topologies can be produced in gauge-mediated supersymmetry models in which pair-produced gluinos or squarks decay to photons and gravitinos via short-lived neutralinos. The data sample corresponds to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at s=13 $$ \sqrt{s}=13 $$ TeV recorded by the CMS experiment at the LHC in 2016. No significant excess of events above the expected standard model background is observed. The data are interpreted in simplified models of gluino and squark pair production, in which gluinos or squarks decay via neutralinos to photons. Gluino masses of up to 1.50-2.00 TeV and squark masses up to 1.30-1.65 TeV are excluded at 95% confidence level, depending on the neutralino mass and branching fraction.
Abstract A study of the associated production of a $$\mathrm{Z} $$ Z boson and a charm quark jet ($$\mathrm{Z} + \mathrm{c} $$ Z+c ), and a comparison to production with a $$\mathrm{b} $$ b quark jet ...($$\mathrm{Z} + \mathrm{b} $$ Z+b ), in $$\mathrm {p}\mathrm {p}$$ pp collisions at a centre-of-mass energy of 8$$\,\text {TeV}$$ TeV are presented. The analysis uses a data sample corresponding to an integrated luminosity of 19.7$$\,\text {fb}^{-1}$$ fb-1 , collected with the CMS detector at the CERN LHC. The $$\mathrm{Z} $$ Z boson candidates are identified through their decays into pairs of electrons or muons. Jets originating from heavy flavour quarks are identified using semileptonic decays of $$\mathrm{c} $$ c or $$\mathrm{b} $$ b flavoured hadrons and hadronic decays of charm hadrons. The measurements are performed in the kinematic region with two leptons with $$p_{\mathrm {T}} ^{\ell } > 20\,\text {GeV} $$ pTℓ>20GeV , $${|\eta ^{\ell }|} < 2.1$$ |ηℓ|<2.1 , $$71< m_{\ell \ell } < 111\,\text {GeV} $$ 71<mℓℓ<111GeV , and heavy flavour jets with $$p_{\mathrm {T}} ^{\text {jet}} > 25\,\text {GeV} $$ pTjet>25GeV and $${|\eta ^{ \text {jet}}|} < 2.5$$ |ηjet|<2.5 . The $$\mathrm{Z} + \mathrm{c} $$ Z+c production cross section is measured to be $$\sigma (\mathrm {p}\mathrm {p}\rightarrow \mathrm{Z} + \mathrm{c} + X) \mathcal {B}(\mathrm{Z} \rightarrow \ell ^+\ell ^-) = 8.8 \pm 0.5\,\text {(stat)} \pm 0.6\,\text {(syst)} \,\text {pb} $$ σ(pp→Z+c+X)B(Z→ℓ+ℓ-)=8.8±0.5(stat)±0.6(syst)pb . The ratio of the $$\mathrm{Z} + \mathrm{c} $$ Z+c and $$\mathrm{Z} + \mathrm{b} $$ Z+b production cross sections is measured to be $$\sigma (\mathrm {p}\mathrm {p}\rightarrow \mathrm{Z} + \mathrm{c} + X)/\sigma (\mathrm {p}\mathrm {p}\rightarrow \mathrm{Z} + \mathrm{b} + X) = 2.0 \pm 0.2\,\text {(stat)} \pm 0.2\,\text {(syst)} $$ σ(pp→Z+c+X)/σ(pp→Z+b+X)=2.0±0.2(stat)±0.2(syst) . The $$\mathrm{Z} + \mathrm{c} $$ Z+c production cross section and the cross section ratio are also measured as a function of the transverse momentum of the $$\mathrm{Z} $$ Z boson and of the heavy flavour jet. The measurements are compared with theoretical predictions.
Abstract A search for new physics in events with a Z boson produced in association with large missing transverse momentum at the LHC is presented. The search is based on the 2016 data sample of ...proton-proton collisions recorded with the CMS experiment at $$\sqrt{s} = 13\,\text {TeV} $$ s=13TeV , corresponding to an integrated luminosity of 35.9$$\,\text {fb}^{-1}$$ fb-1 . The results of this search are interpreted in terms of a simplified model of dark matter production via spin-0 or spin-1 mediators, a scenario with a standard-model-like Higgs boson produced in association with the Z boson and decaying invisibly, a model of unparticle production, and a model with large extra spatial dimensions. No significant deviations from the background expectations are found, and limits are set on relevant model parameters, significantly extending the results previously achieved in this channel.
Nitrate Biosynthesis in Man Green, Laura C.; De Luzuriaga, Katherine Ruiz; Wagner, David A. ...
Proceedings of the National Academy of Sciences - PNAS,
12/1981, Letnik:
78, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Nitrate metabolism was investigated in longterm metabolic balance studies on healthy young men. Under conditions of constant low ingestion of nitrate (< 180 μ mol/day per subject), the amount of ...nitrate excreted in urine was an average of 4-fold greater than the amount ingested. Balance studies with15NO3
-showed that the source of the excess nitrate in urine was the endogenous biosynthesis of nitrate, rather than the emptying of a body pool. Nitrate biosynthesis occurred when nitrate ingestion was high as well as low, and the amounts synthesized appeared to be independent of intake and comparable to the amounts ingested from normal diets. Analysis of the15NO3
-data also revealed that half of ingested nitrate was recovered as urinary nitrate. Because nitrate in urine is the net result of (i) intake, (ii) endogenous synthesis, and (iii) metabolic losses, the magnitude of the losses is such that, despite ongoing synthesis, the amount of nitrate in the urine of people consuming most diets will be less than the amount ingested.
Abstract The differential cross section for inclusive particle production as a function of energy in proton-proton collisions at a center-of-mass energy of 13 TeV is measured in the very forward ...region of the CMS detector. The measurement is based on data collected with the CMS apparatus at the LHC, and corresponds to an integrated luminosity of 0.34 μb−1. The energy is measured in the CASTOR calorimeter, which covers the pseudorapidity region −6.6 < η < −5.2. The results are given as a function of the total energy deposited in CASTOR, as well as of its electromagnetic and hadronic components. The spectra are sensitive to the modeling of multiparton interactions in pp collisions, and provide new constraints for hadronic interaction models used in collider and in high energy cosmic ray physics.
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