scholarly journals New project for precise neutron lifetime measurement at J-PARC

2019 ◽  
Vol 219 ◽  
pp. 03003 ◽  
Author(s):  
Naoki Nagakura ◽  
Katsuya Hirota ◽  
Sei Ieki ◽  
Takashi Ino ◽  
Yoshihisa Iwashita ◽  
...  
Keyword(s):  
Big Bang ◽  
Proton Accelerator ◽  
Neutron Lifetime ◽  
Big Bang Nucleosynthesis ◽  
Cold Neutrons ◽  
Beam Experiment ◽  
Research Complex ◽  
Time Projection ◽  
Beta Decays

The decay lifetime of free neutrons (∼880 s) is an important parameter of the weak interaction and for Big Bang Nucleosynthesis. However, results of measurements currently show discrepancies depending on the method used. As most experiments nowadays employ ultra cold neutrons, we have developed a new cold-beam experiment which we perform at the Japan Proton Accelerator Research Complex. As a special feature, a polarized neutron beam is bunched by a spin flip chopper. A time projection chamber operated with He and CO2 gas, including a well-controlled amount of 3He, is used for detection of the beta-decays and simultaneous determination of the beam intensity. Using the data between 2014 and 2016, we evaluated our first, preliminary result of the neutron lifetime as 896 ± 10(stat.) −10+14(sys.) s. We plan several upgrades to achieve our precision goal of 1 s.

scholarly journals Neutron lifetime measurement with pulsed cold neutrons

2020 ◽  
Author(s):  
K Hirota ◽  
G Ichikawa ◽  
S Ieki ◽  
T Ino ◽  
Y Iwashita ◽  
...  
Keyword(s):  
Decay Rate ◽  
Reaction Rate ◽  
Proton Accelerator ◽  
Neutron Decay ◽  
Spallation Neutron Source ◽  
Neutron Lifetime ◽  
Cold Neutrons ◽  
Research Complex ◽  
Gas Chamber ◽  
Pulsed Neutron

Abstract The neutron lifetime has been measured by comparing the decay rate with the reaction rate of 3He nuclei of a pulsed neutron beam from the spallation neutron source at the Japan Proton Accelerator Research Complex (J-PARC). The decay rate and the reaction rate were determined by simultaneously detecting electrons from the neutron decay and protons from the 3He(n, p) 3H reaction using a gas chamber of which working gas contains diluted 3He. The measured neutron lifetime was 898 ± 10stat+15−18sys s.

scholarly journals Progress on the BL2 beam measurement of the neutron lifetime

2019 ◽  
Vol 219 ◽  
pp. 03002 ◽  
Author(s):  
Shannon F. Hoogerheide ◽  
Jimmy Caylor ◽  
Evan R. Adamek ◽  
Eamon S. Anderson ◽  
Ripan Biswas ◽  
...  
Keyword(s):  
Light Element ◽  
Big Bang ◽  
Neutron Lifetime ◽  
Big Bang Nucleosynthesis ◽  
Element Abundances ◽  
Cold Neutron Beam ◽  
The Standard Model ◽  
Systematic Effects ◽  
Mixing Matrix ◽  
Beam Technique

A precise value of the neutron lifetime is important in several areas of physics, including determinations of the quark-mixing matrix element |Vud|, related tests of the Standard Model, and predictions of light element abundances in Big Bang Nucleosynthesis models. We report the progress on a new measurement of the neutron lifetime utilizing the cold neutron beam technique. Several experimental improvements in both neutron and proton counting that have been developed over the last decade are presented. This new effort should yield a final uncertainty on the lifetime of 1 s with an improved understanding of the systematic effects.

scholarly journals Improved accuracy in the determination of the thermal cross section of ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ for neutron lifetime measurement

2019 ◽  
Vol 2019 (9) ◽  
Author(s):  
R Kitahara ◽  
K Hirota ◽  
S Ieki ◽  
T Ino ◽  
Y Iwashita ◽  
...  
Keyword(s):  
Cross Section ◽  
Lifetime Measurement ◽  
Reaction Cross ◽  
Proton Accelerator ◽  
Incident Neutron ◽  
Neutron Lifetime ◽  
The Cross ◽  
Thermal Cross Section ◽  
Improved Accuracy

Abstract In a neutron lifetime measurement at the Japan Proton Accelerator Complex, the neutron lifetime is calculated from the neutron decay rate and the incident neutron flux. The flux is obtained by counting the protons emitted from the neutron absorption reaction of ${}^{3}{\rm He}$ gas, which is diluted in a mixture of working gas in a detector. Hence, it is crucial to determine the amount of ${}^{3}{\rm He}$ in the mixture. In order to improve the accuracy of the number density of the ${}^{3}{\rm He}$ nuclei, we have suggested using the ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ reaction as a reference because this reaction involves similar kinetic energy to the $^3$He(n,p)$^3$H reaction and a smaller reaction cross section to introduce reasonable large partial pressure. The uncertainty of the recommended value of the cross section, however, is not satisfied with our requirement. In this paper we report the most accurate experimental value of the cross section of the $^{14}$N(n,p)$^{14}$C reaction at a neutron velocity of 2200 m s$^{-1}$, measured relative to the $^3$He(n,p)$^3$H reaction. The result was 1.868 $\pm$ 0.003 (stat.) $\pm$ 0.006 (sys.) b. Additionally, the cross section of the $^{17}$O(n,$\alpha$)$^{14}$C reaction at the neutron velocity is also redetermined as 249 $\pm$ 6 mb.

scholarly journals Big bang nucleosynthesis: an accurate determination of light element yields

2000 ◽  
Vol 568 (1-2) ◽  
pp. 421-444 ◽  
Author(s):  
S. Esposito ◽  
G. Mangano ◽  
G. Miele ◽  
O. Pisanti
Keyword(s):  
Accurate Determination ◽  
Light Element ◽  
Big Bang ◽  
Big Bang Nucleosynthesis

Big bang nucleosynthesis with a new neutron lifetime

2005 ◽  
Vol 71 (2) ◽  
Author(s):  
G. J. Mathews ◽  
T. Kajino ◽  
T. Shima
Keyword(s):  
Big Bang ◽  
Neutron Lifetime ◽  
Big Bang Nucleosynthesis

scholarly journals A new tension in the cosmological model from primordial deuterium?

2021 ◽  
Vol 502 (2) ◽  
pp. 2474-2481
Author(s):  
Cyril Pitrou ◽  
Alain Coc ◽  
Jean-Philippe Uzan ◽  
Elisabeth Vangioni
Keyword(s):  
Big Bang ◽  
Reaction Cross ◽  
Light Elements ◽  
Neutron Lifetime ◽  
Microwave Background ◽  
Big Bang Nucleosynthesis ◽  
Baryonic Density ◽  
The Status ◽  
Big Bang Model ◽  
The Big Bang

ABSTRACT Recent measurements of the D(p,γ)3He nuclear reaction cross-section and of the neutron lifetime, along with the reevaluation of the cosmological baryon abundance from cosmic microwave background (CMB) analysis, call for an update of abundance predictions for light elements produced during the big-bang nucleosynthesis (BBN). While considered as a pillar of the hot big-bang model in its early days, BBN constraining power mostly rests on deuterium abundance. We point out a new ≃1.8σ tension on the baryonic density, or equivalently on the D/H abundance, between the value inferred on one hand from the analysis of the primordial abundances of light elements and, on the other hand, from the combination of CMB and baryonic oscillation data. This draws the attention on this sector of the theory and gives us the opportunity to reevaluate the status of BBN in the context of precision cosmology. Finally, this paper presents an upgrade of the BBN code primat.

BIG BANG NUCLEOSYNTHESIS: AN UPDATE

1996 ◽  
Vol 11 (03) ◽  
pp. 409-428 ◽  
Author(s):  
KEITH A. OLIVE ◽  
SEAN T. SCULLY
Keyword(s):  
Standard Model ◽  
Light Element ◽  
Big Bang ◽  
Current Status ◽  
Beyond The Standard Model ◽  
Effective Number ◽  
Big Bang Nucleosynthesis ◽  
Element Abundances ◽  
The Standard Model

The current status of big bang nucleosynthesis is reviewed with an emphasis on the comparison between the observational determination of the light element abundances of D , 3 He , 4 He and 7 Li and the predictions from theory. In particular, we present new analyses for 4 He and 7 Li . Implications for physics beyond the standard model are also discussed. In addition, limits on the effective number of neutrino flavors are updated.

scholarly journals The effects of coupling variations on BBN

2009 ◽  
Vol 5 (H15) ◽  
pp. 305-305
Author(s):  
Keith A. Olive
Keyword(s):  
Binding Energy ◽  
Mass Difference ◽  
Big Bang ◽  
Neutron Lifetime ◽  
Big Bang Nucleosynthesis ◽  
Fundamental Parameters ◽  
Proton Mass ◽  
Unified Theories

AbstractThe effect of variations of the fundamental nuclear parameters on big-bang nucleosynthesis are modeled and discussed in detail taking into account the interrelations between the fundamental parameters arising in unified theories. Considering only 4He, strong constraints on the variation of the neutron lifetime, neutron-proton mass difference are set. We show that a variation of the deuterium binding energy is able to reconcile the 7Li abundance deduced from the WMAP analysis with its spectroscopically determined value while maintaining concordance with D and 4He.

scholarly journals Revisiting cosmic microwave background radiation using blackbody radiation inversion

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Koustav Konar ◽  
Kingshuk Bose ◽  
R. K. Paul
Keyword(s):  
Temperature Distribution ◽  
Cosmic Microwave Background ◽  
Background Radiation ◽  
Big Bang ◽  
Blackbody Radiation ◽  
Microwave Background ◽  
Background Spectrum ◽  
Microwave Background Radiation ◽  
Mathematical Process

AbstractBlackbody radiation inversion is a mathematical process for the determination of probability distribution of temperature from measured radiated power spectrum. In this paper a simple and stable blackbody radiation inversion is achieved by using an analytical function with three determinable parameters for temperature distribution. This inversion technique is used to invert the blackbody radiation field of the cosmic microwave background, the remnant radiation of the hot big bang, to infer the temperature distribution of the generating medium. The salient features of this distribution are investigated and analysis of this distribution predicts the presence of distortion in the cosmic microwave background spectrum.

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