Measurement of hadron composition in charged jets from pp collisions with the ALICE experiment

We report the first measurement of charged pion, kaon and (anti-)proton production in jets from hadron colliders. The measurement was carried out with the ALICE detector using $2\times10^8$ minimum bias pp collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the LHC. We present the $\pi$, K and p transverse momentum ($p_\textrm{T}$) spectra, as well as the spectra of the reduced momentum (${z^\textrm{ch}\equiv p_\textrm{T}^\textrm{track}/p_\textrm{T, jet}^\textrm{ch}}$), in charged jets of $p_\textrm{T}$ between 5--20 $\textrm{GeV}/c$. The measurement is compared to Monte Carlo calculations.Comment: 4 pages, 4 figures, Proceedings of XXIV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2014), May 19-24, 2014, Darmstad

Exploring the performance limits of the ALICE Time Projection Chamber and Transition Radiation Detector for measuring identified hadron production at the LHC

The Time Projection Chamber (TPC) and Transition Radiation Detector (TRD) are the main tracking and particle identification devices in the ALICE experiment at the CERN LHC. This thesis studies aspects of their performance beyond the original designs. This includes extending the TPC momentum measurement for cosmic rays to sub-TeV scale, investigating a robust identification method for electrons and hadrons by the TRD, and developing new approaches to characterize the TPC and TRD signals. These studies lead to an intriguing observation of the transition radiation from sub-TeV cosmic muons, and a universal method -- the TPC coherent fit -- to extract yields of different particle species with momentum from 0.5 to above 20 GeV/c. With the TPC coherent fit, transverse momentum spectra (0.6 < pt < 20 GeV/c) of pions, kaons and protons at mid-rapidity (|y|<~0.8) in pp collisions at sqrt(s) = 2.76 and 7 TeV and Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV at the LHC are measured. In this unified approach both the anomalous enhancement of the proton-to-pion ratio at moderate pt (2-8 GeV/c) (the so-called baryon anomaly) and the nuclear modification of particle yields up to high pt (> 10 GeV/c) in Pb-Pb collisions are observed. The particle production is also studied in jets from pp collisions at 7 TeV and the results are well described by Perugia-0 tune of PYTHIA6

Pion-proton correlation in neutrino interactions on nuclei

In neutrino-nucleus interactions, a proton produced with a correlated pion might exhibit a left-right asymmetry relative to the lepton scattering plane even when the pion is absorbed. Absent in other proton production mechanisms, such an asymmetry measured in charged-current pionless production could reveal the details of the absorbed-pion events that are otherwise inaccessible. In this study, we demonstrate the idea of using final-state proton left-right asymmetries to quantify the absorbed-pion event fraction and underlying kinematics. This technique might provide critical information that helps constrain all underlying channels in neutrino-nucleus interactions in the GeV regime.Comment: 7 pages, 4 figure

Probing Nuclear Effects at the T2K Near Detector Using Single-Transverse Kinematic Imbalance

In order to make precision measurements of neutrino oscillations using few-GeV neutrino beams a detailed understanding of nuclear effects in neutrino scattering is essential. Recent studies have revealed that single-transverse kinematic imbalance (STKI), defined in the plane transverse to an incoming neutrino beam, can act as a unique probe of these nuclear effects. This work first illustrates that an exclusive measurement of STKI at the off-axis near detector of the T2K experiment (ND280) is expected to distinguish the presence of interactions with two nucleons producing two holes (2p-2h) from alterations of the predominant underlying cross-section parameter (MA- the nucleon axial mass). Such a measurement is then demonstrated with fake data, showing substantial nuclear model separation potential

Abundance changes of marsh plant species over 40 years are better explained by niche position water level than functional traits

Acknowledgements: This study was supported by the National Natural Science Foundation of China (grants No.41671109 and 41371107) and by the Natural Science Foundation of Jilin Province (grant No. 20190201281JC). We thank Xiaofeng Xu for the suggestions and Håkan Rydin for the comments on the manuscript.Peer reviewedPostprin

Effect of hydrological fluctuation on nutrient stoichiometry and trade-offs of Carex schmidtii

Nutrient stoichiometry and trade-offs focusing on the mass balance of multiple nutrient elements play important roles in the response mechanism of plants to environmental stresses in wetlands. Nonetheless, little is known about the response dynamics and trade-offs of nutrient elements of wetland plants, especially potassium (K), under hydrological fluctuation conditions. Greenhouse experiments have been undertaken to assess the effects of initial water level (DW), water-level amplitude (AW), lasted time and their interactions on the response processes of nutrient stoichiometry of Carex schmidtii. Plant nutrient trade-offs and limitation were investigated under multiple hydrological fluctuation conditions. Results showed that plant nitrogen (N), K and their ratio were significantly influenced by DW. Lasted time significantly affected nutrient stoichiometry except for N:P ratio. Plant N:K ratio were sensitive to the three factors and their interactions. Moreover, plant N:P and N:K ratios indicated a significant P limitation and K limitation for the growth of C. schmidtii, respectively. The scaling exponents showed that DW, AW and their interaction have significant effects on the relationships of P ~ N, K ~ N and K ~ P. Principal component analysis indicated that lasted time had significant effects on the nutrient balances. Hydrological fluctuation resulted in changes in plant nutrients and their ratios, but nutrient trade-offs relieved the negative effects. These findings help in understanding the nutrient stoichiometry and response mechanism of C. schmidtii to hydrological fluctuation and provide invaluable information for nutrient and hydrological management for tussock wetlands