13,145 research outputs found

    A Short Proof of Gamas's Theorem

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    If \chi^\lambda is the irreducible character of the symmetric group S_n corresponding to the partition \lambda of n then we may symmetrize a tensor v_1 \otimes ... \otimes v_n by \chi^\lambda. Gamas's theorem states that the result is not zero if and only if we can partition the set {v_i} into linearly independent sets whose sizes are the parts of the transpose of \lambda. We give a short and self-contained proof of this fact

    Strange Quark Contribution to the Proton Spin, from Elastic ep\vec{e}p and νp\nu p Scattering

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    The strangeness contribution to the vector and axial form factors of the proton is presented for momentum transfers in the range 0.45 < Q2Q^2 < 1.0 GeV2^2. The results are obtained via a combined analysis of forward-scattering parity-violating elastic ep\vec{e}p asymmetry data from the G0 and HAPPEx experiments at Jefferson Lab, and elastic νp\nu p and νˉp\bar{\nu}p scattering data from Experiment 734 at Brookhaven National Laboratory. The combination of the two data sets allows for the simultaneous extraction of GEsG_E^s, GMsG_M^s, and GAsG_A^s over a significant range of Q2Q^2 for the very first time. Determination of the strange axial form factor GAsG_A^s is vital to an understanding of the strange quark contribution to the proton spin.Comment: 4 pages, 1 figure; proceedings for SPIN 2006; will be published in AIP Conference Proceeding

    PHENIX Measurement of Parity-Violating Single Spin Asymmetry in W Production in p+p Collisions at 500 GeV

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    The flavor-separated polarized parton distribution functions for light quarks and anti-quarks in the proton can be studied in the production of WW bosons in pp+pp collisions. The WWs are produced in processes like u+dˉW+u+\bar{d}\rightarrow W^+ and uˉ+dW\bar{u}+ d \rightarrow W^- and we observe the lepton (an electron or muon) from the decay channel W±l±νW^{\pm}\rightarrow l^{\pm}\nu. The electron energy spectrum from WW decays measured with an integrated luminosity of approximately 10 pb1^{-1} will be shown, with a measurement of the electron single spin asymmetry in central rapidity.Comment: Proceedings of the DIFFRACTION 2010 Conference; 4 pages, 2 figure

    Progress On Neutrino-Proton Neutral-Current Scattering In MicroBooNE

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    The MicroBooNE Experiment at the Fermi National Accelerator Laboratory, an 89-ton active mass liquid argon time projection chamber, affords a unique opportunity to observe low-Q2Q^2 neutral-current neutrino-proton scattering events. Neutral-current neutrino-proton scattering at Q2<1Q^2 < 1 GeV2^2 is dominated by the proton's axial form factor, which can be written as a combination of contributions from the up, down, and strange quarks: GA(Q2)=12[GAu(Q2)+GAd(Q2)+GAs(Q2)]G_A(Q^2) = \frac{1}{2}[-G_A^u(Q^2)+G_A^d(Q^2)+G_A^s(Q^2)]. The contribution from up and down quarks has been established in past charged-current measurements. The contribution from strange quarks at low Q2Q^2 remains unmeasured; this is of great interest since the strange quark contribution to the proton spin can be determined from the low-Q2Q^2 behavior: ΔS=GAs(Q2=0)\Delta S = G_A^s(Q^2=0). MicroBooNE began operating in the Booster Neutrino Beam in October 2015. I will present the status in observing isolated proton tracks in the MicroBooNE detector as a signature for neutral-current neutrino-proton events. The sensitivity of the MicroBooNE experiment for measuring the strange quark contribution to the proton spin will be discussed.Comment: Proceedings for the 26th International Nuclear Physics Conference, 11-16 September, 2016, Adelaide, Australi

    Predictability effects in adult-directed and infant-directed speech: Does the listener matter?

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    A well-known effect in speech production is that more predictable words tend to be phonetically reduced. Recent work has suggested that predictability effects result from hardwired properties of the language production system, rather than active modulation by the talker to accommodate the listener. However, these studies investigated only minor manipulations of listener characteristics. Here, we examine predictability effects with two very different listener populations: adults and preverbal infants. Using mixed effects regressions on spontaneous speech corpora, we compare the effect of word frequency, probability in context, and previous mention on word duration in adult-directed and infant-directed speech. We find that the effects of preceding context and word frequency differ according to listener. Contrary to previous work, these results suggest that talkers do modulate the phonetic effects of predictability based on listener characteristics. To our knowledge, this study is also the first published analysis of predictability effects in infant-directed speech

    Unsupervised syntactic chunking with acoustic cues: Computational models for prosodic bootstrapping

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    Learning to group words into phrases without supervision is a hard task for NLP systems, but infants routinely accomplish it. We hypothesize that infants use acoustic cues to prosody, which NLP systems typically ignore. To evaluate the utility of prosodic information for phrase discovery, we present an HMM-based unsupervised chunker that learns from only transcribed words and raw acoustic correlates to prosody. Unlike previous work on unsupervised parsing and chunking, we use neither gold standard part-of-speech tags nor punctuation in the input. Evaluated on the Switchboard corpus, our model outperforms several baselines that exploit either lexical or prosodic information alone, and, despite producing a flat structure, performs competitively with a state-of-the-art unsupervised lexicalized parser, with a substantial advantage in precision. Our results support the hypothesis that acoustic-prosodic cues provide useful evidence about syntactic phrases for language-learning infants.10 page(s