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Title: Progress On Neutrino-Proton Neutral-Current Scattering In MicroBooNE

Abstract

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-$Q^2$ neutral-current neutrino-proton scattering events. Neutral-current neutrino-proton scattering at $Q^2 < 1$ GeV$^2$ 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: $$G_A(Q^2) = \frac{1}{2}[-G_A^u(Q^2)+G_A^d(Q^2)+G_A^s(Q^2)]$$. The contribution from up and down quarks has been established in past charged-current measurements. The contribution from strange quarks at low $Q^2$ remains unmeasured; this is of great interest since the strange quark contribution to the proton spin can be determined from the low-$Q^2$ behavior: $$\Delta S = G_A^s(Q^2=0)$$. 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.

Authors:
ORCiD logo [1]
  1. New Mexico State U.
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Org.:
MicroBooNE
OSTI Identifier:
1347128
Report Number(s):
arXiv:1701.04483; FERMILAB-CONF-17-035-ND
1509370
DOE Contract Number:
AC02-07CH11359
Resource Type:
Conference
Resource Relation:
Conference: 26th International Nuclear Physics Conference, Adelaide, Australia, 09/11-09/16/2016
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Pate, Stephen. Progress On Neutrino-Proton Neutral-Current Scattering In MicroBooNE. United States: N. p., 2017. Web.
Pate, Stephen. Progress On Neutrino-Proton Neutral-Current Scattering In MicroBooNE. United States.
Pate, Stephen. Mon . "Progress On Neutrino-Proton Neutral-Current Scattering In MicroBooNE". United States. doi:. https://www.osti.gov/servlets/purl/1347128.
@article{osti_1347128,
title = {Progress On Neutrino-Proton Neutral-Current Scattering In MicroBooNE},
author = {Pate, Stephen},
abstractNote = {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-$Q^2$ neutral-current neutrino-proton scattering events. Neutral-current neutrino-proton scattering at $Q^2 < 1$ GeV$^2$ 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: $G_A(Q^2) = \frac{1}{2}[-G_A^u(Q^2)+G_A^d(Q^2)+G_A^s(Q^2)]$. The contribution from up and down quarks has been established in past charged-current measurements. The contribution from strange quarks at low $Q^2$ remains unmeasured; this is of great interest since the strange quark contribution to the proton spin can be determined from the low-$Q^2$ behavior: $\Delta S = G_A^s(Q^2=0)$. 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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 16 00:00:00 EST 2017},
month = {Mon Jan 16 00:00:00 EST 2017}
}

Conference:
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  • The net contribution of the strange quark spins to the proton spin,more » $$\Delta s$$, can be determined from neutral current elastic neutrino-proton interactions at low momentum transfer combined with data from electron-proton scattering. The probability of neutrino-proton interactions depends in part on the axial form factor, which represents the spin structure of the proton and can be separated into its quark flavor contributions. Low momentum transfer neutrino neutral current interactions can be measured in MicroBooNE, a high-resolution liquid argon time projection chamber (LArTPC) in its first year of running in the Booster Neutrino Beamline at Fermilab. The signal for these interactions in MicroBooNE is a single short proton track. We present our work on the automated reconstruction and classification of proton tracks in LArTPCs, an important step in the determination of neutrino- nucleon cross sections and the measurement of $$\Delta s$$.« less
  • Distributions of dN/dQ/sup 2/ for approximately 150 events of the process ..nu../sub u/p ..-->.. ..nu../sup u/p and for approximately 40 events of anti ..nu../sup u/p ..-->.. anti ..nu../sup u/p are shown in the region 0.35 equal to or less than Q/sup 2/ equal to or less than 0.9 (GeV,c)/sup 2/ where -Q/sup 2/ is the square of the four momentum transferred from the incident neutrino to the proton. Preliminary estimates of the weak neutral current to weak charged current ratios from these data are consistent with the values of R/sub ..nu../ = 0.17 +- 0.05 and R/sub anti ..nu../ =more » 0.2 +- 0.1 measured previously.« less
  • Micro Booster Neutrino Experiment (MicroBooNE) is a Liquid Argon Time Projection Chamber (LArTPC) operating in the Booster Neutrino Beamline at Fermi National Accelerator Laboratory. MicroBooNE's physics goals include studying short baslinemore » $$\nu$$ oscillation and performing a suite of low energy $$\nu$$ cross section measurements. Of particular interest to MicroBooNE, and the broader LArTPC community, are electromagnetic showers; these showers are at the heart of searches for charged current $$\nu_e$$ interactions, including MicroBooNE's flagship search for a MiniBooNE-like low energy excess (LEE). Neutral current $$\pi^0$$'s, which decay into 2 electromagnetic showers ($$\gamma$$'s), are the dominant source of non-$$\nu_e$$ backgrounds in searches for $$\nu_{\mu}\rightarrow\nu_e$$ oscillations in LArTPCs, such as the LEE. While precise measurements of this neutral current channel will provide a tight constraint on our modeling uncertainties, such events are particularly difficult to iden tify in data with our current tools, as there is often little or no activity at the neutrino interaction point. Charged current interactions, on the other hand, have simpler topologies with a long $$\mu$$ track that anchors to the interaction vertex. With a vertex in hand, we can develop automated reconstruction tools for neutrino-induced shower topologies (like the $$\gamma$$'s from $$\pi^0$$ decay). Thus, in studying charged current $$\pi^0$$ interactions, we are developing tools that can potentially be used to reconstruct an important LEE background, while also studying the physics of neutrino interactions, of which data is sparse for argon. This thesis reports the world's first measurement of the absolute, flux-averaged cross section of $$\nu_{\mu}$$-charged current single $$\pi^0$$ production on argon. The analysis chain begins with the selection of inclusive $$\nu_\mu$$ charged current events, where a candidate $$\mu$$ and neutrino interaction vertex are identified. These events are t hen passed to a reconstruction framework where electromagnet! ic shower candidates are reconstructed using computer visualization tools. Finally, the cross section is calculated on two reconstructed topologies: those with at least two reconstructed showers and those with at least one. Additionally, this work describes the first fully-automated electromagnetic shower reconstruction process employed by a LArTPC to perform a cross section analysis. We measure the flux averaged cross section on argon at 824 MeV via the two and one shower selections respectively to be \par \noindent $$\sigma_{\geq2 Shower}$$ = (2.56 $$\pm$$ $$0.50_{stat}$$ $$\pm$$ $$0.31_{genie}$$ $$\pm$$ $$0.37_{flux}$$ $$\pm$$ $$0.31_{det}$$) $$\times$$ $$10^{-38}$$ $$\frac{cm^2}{Ar}$$, \par \noindent $$\sigma_{\geq 1 Shower}$$ = (2.64 $$\pm$$ $$0.33_{stat}$$ $$\pm$$ $$0.36_{genie}$$ $$\pm$$ $$0.38_{flux}$$ $$\pm$$ $$0.35_{det}$$) $$\times$$ $$10^{-38}$$ $$\frac{cm^2}{Ar}$$.« less
  • It may appear unusual to have a contribution on neutrino scattering at a school devoted to electromagnetic probes, as the neutrino has no known electromagnetic couplings. However, as a means to examine the hidden flavor currents in the nucleon, the recent results observed for the spin structure function of the nucleon have focused attention on the nucleon`s neutral weak currents (NWC). When an electromagnetic probe is scattered elastically from a nucleon, the NWC interactions are observable only through the detection of very small (> 10{sup {minus}6}) parity-violating processes. In the case of neutrino scattering, the NWC is the dominant coupling.more » In what follows it will be shown how the nucleon`s vector and axial vector form factors arising from strange quark currents can be measured via neutrino elastic scattering. Preliminary results from the Large Scintillation Neutrino Detector (LSND) at LAMPF will be presented as well as a recent analysis of an earlier experiment (E734) carried out at Brookhaven.« less