Evaluation of pre-screened sweet potato germplasm for biomass production under different cropping regimes and their potential as dual-purpose varieties in Kenya.

Six cultivars of sweet potato were grown on farms in five sites located in central, south and north rift valley regions of Kenya under rain fed conditions. Two sites each were located in the high and medium altitude areas while one was located in the low altitude area. All sites have warm climates except one in the high altitude that experiences cold climate. The cultivars included 103001, Gweri, Kemb 23, Kemb 36, Naspot 1 and Wagabolige. The vines of each variety were harvested at two different stages (75 and 150 days) post planting. The 75-day treatment was ratooned again at 150 day post planting. Agronomical observations were carried during the long rains seaso 2010. Harvesting vines twice significantly (P<001) increased forage yields but significantly (P<001) reduced root yield in all varieties. The Gweri variety realized the highest forage but lowest storage root yields indicating its potential as a forage variety. Kemb 23, Kemb 36 and Napsot 1 produced appreciable amount of vines and highest root storage yield making them potential dual purpose varieties. The effect of agro ecological zone (AEZ) varied with time of harvest. There was less interaction between the cultivars and the AEZ at 75 day harvest. Gweri, Kemb 23 and Kemb 36 showed some level of interaction with AEZ at 150 day harvest. Across AEZs dry vine yields (t DM/ha) ranged from 2.3,5.3 in 103001, 2.4,8.5 in Gweri, 1.9,8.4 in Kemb 23, 1.4,7.8 in Kemb 36, 1.8,7.4 in Naspot 1 and 1.2,7.4 in Wagabolige and dry storage root yields (t DM/ha) ranged from 0.7,2 in 103001, 0.3,1.2 in Gweri, 0.4,2.5 in Kemb 23, 0.9,1.5 in Kemb 36 , 1.7,2.3 in Naspot 1 and 0.5,1.8 in Wagabolige. The storage root yield: vine (R/V) ratio was determined by dividing the total root by vine dry matter yield. The R/V ratios significantly (P<005) varied between cultivar and harvesting stage. The mean R/V were 1.8 in 103001, 0.2 in Gweri, 0.6 in Kemb 23, 0.5 in Kemb 36, 1.5 in Naspot 1 and 0.7 in Wagabolige. The R/V ratios obtained classifies 103001 and Naspot 1 as low forage-high root production varieties, Wagabolige and Kemb 36 as low dual purpose and Kemb 36 and Gweri as forage varieties. Preference of different growers for forage vs. dual purpose types appears to vary by location

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

The Physics of Star Cluster Formation and Evolution

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe

Performance of the CMS Level-1 trigger in proton-proton collisions at √s = 13 TeV

At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-of-mass energy of 13\TeV. During Run 2 (years 2015–2018) the LHC eventually reached a luminosity of 2.1× 10$^{34}$ cm$^{-2}$s$^{-1}$, almost three times that reached during Run 1 (2009–2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016–2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals

Studies of jet quenching using isolated-photon + jet correlations in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV

Results from the first study of isolated-photon + jet correlations in relativistic heavy ion collisions are reported. The analysis uses data from PbPb collisions at a centre-of-mass energy of 2.76 TeV per nucleon pair corresponding to an integrated luminosity of 150 inverse microbarns recorded by the CMS experiment at the LHC. For events containing an isolated photon with transverse momentum pt(gamma) > 60 GeV and an associated jet with pt(Jet) > 30 GeV, the photon + jet pt imbalance is studied as a function of collision centrality and compared to pp data and PYTHIA calculations at the same collision energy. Using the pt(gamma) of the isolated photon as an estimate of the momentum of the associated parton at production, this measurement allows an unbiased characterisation of the in-medium parton energy loss. For more central PbPb collisions, a significant decrease in the ratio pt(Jet)/pt(gamma) relative to that in the PYTHIA reference is observed. Furthermore, significantly more pt(gamma) > 60 GeV photons in PbPb are observed not to have an associated pt(Jet) > 30 GeV jet, compared to the reference. However, no significant broadening of the photon + jet azimuthal correlation is observed.Comment: Submitted to Physics Letters

Search for jet extinction in the inclusive jet-pT spectrum from proton-proton collisions at s=8 TeV

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.The first search at the LHC for the extinction of QCD jet production is presented, using data collected with the CMS detector corresponding to an integrated luminosity of 10.7  fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The extinction model studied in this analysis is motivated by the search for signatures of strong gravity at the TeV scale (terascale gravity) and assumes the existence of string couplings in the strong-coupling limit. In this limit, the string model predicts the suppression of all high-transverse-momentum standard model processes, including jet production, beyond a certain energy scale. To test this prediction, the measured transverse-momentum spectrum is compared to the theoretical prediction of the standard model. No significant deficit of events is found at high transverse momentum. A 95% confidence level lower limit of 3.3 TeV is set on the extinction mass scale