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arXiv2014

Measurements of hadron production in p-Pb collisions at LHCf

The transverse momentum distribution for inclusive neutral pions in very forward rapidity region has been measured with the LHCf detector in p-Pb collisions at nucleon-nucleon center-of-mass energies of $\sqrt{s_{NN}}$ = 5.02 TeV at the LHC. The transverse momentum spectra obtained in p-Pb collisions show a strong suppression of the production of neutral pions relative to the spectra in p-p collisions at $\sqrt{s}$ = 5.02 TeV. The nuclear modification factor is about 0.1-0.4, which overall agrees with the predictions of several hadronic interaction Monte Carlo simulations. Furthermore the recent results on the inclusive energy spectra of forward neutrons in p-p collisions at $\sqrt{s}$ = 7 TeV will be discussed.

hep-ex↗

arXiv2014

Proposal; Precise measurements of very forward particle production at RHIC

We propose a new experiment Relativistic Heavy Ion Collider forward (RHICf) for the precise measurements of very forward particle production at RHIC. The proposal is to install the LHCf Arm2 detector in the North side of the ZDC installation slot at the PHENIX interaction point. By installing high-resolution electromagnetic calorimeters at this location we can measure the spectra of photons, neutrons and pi0 at pseudorapidity eta>6.

physics.ins-det↗

arXiv2014

Simulation of the response functions of Extended Range Neutron Multisphere Spectrometer using FLUKA program

In this paper, the distribution of radiation field in the CSNS spectrometer hall was simulated by FLUKA program. The results showed that the radiation field of high energy proton accelerator is dominated by neutron radiation, and the range of neutron energy is quite widely, including about eleven orders of magnitude. Nextly, work of simulation and calculation of the response functions of four Bonner spheres with simplified model is done by FLUKA and MCNP codes respectively, and the acceptable difference proved the feasibility of FLUKA program in this application and the correctness of the relevant calculation method. Through adopting the actual model, we simulate and calculate the energy response functions of Bonner sphere detectors with polyethylene layers of different diameters, including the detectors with lead layers by using FLUKA code. According to the simulation results, we select eleven detectors as the basic structure of ERNMS.

physics.ins-det↗

arXiv2014

Synthesize Neutron-Drip-Line-Nuclides with Free-Neutron Bose-Einstein Condensates Experimentally

We first show a possible way to create a new type of matter, free-neutron Bose-Einstein condensate by the ultracold free-neutron-pair Bose-Einstein condensation and then determine the neutron drip line experimentally. The Bose-Einstein condensation of bosonic and fermionic atoms in atomic gases was performed experimentally and predicted theoretically early. Neutrons are similar to fermionic atoms. We found free neutrons could be cooled to ultracold neutrons with very low energy by other colder neutral atoms which are cooled by the laser. These neutrons form neutron pairs with spin zero, and then ultracold neutron-pairs form Bose-Einstein condensate. Our results demonstrate how these condensates can react with accelerated ion beams at different energy to synthesize very neutron-rich nuclides near, on or/and beyond the neutron drip line, to determine the neutron drip line and whether there are long-life nuclide or isomer islands beyond the neutron drip line experimentally. Otherwise, these experimental results will confirm our prediction that is in the whole interacting region or distance of nuclear force in all energy region from zero to infinite, Only repulsive nuclear force exists among identical nucleons and only among different nucleons exists attractive nuclear force.

nucl-th↗

arXiv2014

Upper limit on the cross section for reactor antineutrinos changing 22Na decay rates

In this paper we present results of a long-term observation of the decay of 22Na in the presence of a nuclear fission reactor. The measurements were made outside the containment wall of and underneath the Koeberg nuclear power plant near Cape Town, South Africa. Antineutrino fluxes ranged from ~5*10^11 to 1.6*10^13 cm^-2 s^-1 during this period. We show that the coincidence summing technique provides a sensitive tool to measure a change in the total decay constant as well as the branching ratio between EC and beta+ decay of 22Na to the first excited state in 22Ne. We observe a relative change in count rate between reactor-ON and reactor-OFF equal to (-0.51+/-0.11)*10^-4. After evaluating possible systematic uncertainties we conclude that the effect is either due to a hidden instrumental cause or due to an interaction between antineutrinos and the 22Na nucleus. An upper limit of ~0.03 barn has been deduced for observing any change in the decay rate of 22Na due to antineutrino interactions.

nucl-ex↗

arXiv2014

A White Paper on SoLID (Solenoidal Large Intensity Device)

In order to fully exploit the physics potential of Jefferson Lab after 12 GeV energy upgrade, a new Solenoidal Large Acceptance Device (SoLID) is proposed. The SoLID spectrometer, with its unique capability of large acceptance and high luminosity, is ideal for precision measurements in semi-inclusive DIS to study transverse spin and transverse-momentum-dependent parton distributions of the nucleon, and for parity-violating Deep Inelastic Scattering (DIS) to perform precision tests of the Standard Model at low energy as well as addressing specific issues in nucleon structure including charge symmetry violation, d/u ratio and higher-twist effects due to di-quark. SoLID is also essential for precision measurements of J/ψelectroproduction in the threshold region to study non-perturbative gluon dynamics and interaction. Five highly rated SoLID experiments and two "run group" experiments have been approved by the JLab Physics Advisory Committee. The physics program is presented along with an overview of the SoLID instrumentation and its current status.

nucl-ex↗

arXiv2014

Hadron production measurements to constrain accelerator neutrino beams

A precise prediction of expected neutrino fluxes is required for a long-baseline accelerator neutrino experiment. The flux is used to measure neutrino cross sections at the near detector, while at the far detector it provides an estimate of the expected signal for the study of neutrino oscillations. In the talk several approaches to constrain the neutrino flux are presented. The first is the traditional one when an interaction chain for the neutrino parent hadrons is stored to be weighted later with real measurements. In this approach differential hadron cross sections are used which, in turn, are measured in ancillary hadron production experiments. The approach is certainly model dependent because it requires an extrapolation to different incident nucleon momenta assuming x_F scaling as well as extrapolation between materials having different atomic numbers. In the second approach one uses a hadron production yields off a real target exploited in the neutrino beamline. Yields of neutrino parent hadrons are parametrized at the surface of the target, thus one avoids to trace the particle interaction history inside the target. As in the case of the first approach, a dedicated ancillary experiment is mandatory. Recent results from the hadron production experiments - NA61/SHINE at CERN (measurements for T2K) and MIPP at Fermilab (measurements for NuMI) - are reviewed.

hep-ex↗

arXiv2014

Underground physics without underground labs: large detectors in solution-mined salt caverns

A number of current physics topics, including long-baseline neutrino physics, proton decay searches, and supernova neutrino searches, hope to someday construct huge (50 kiloton to megaton) particle detectors in shielded, underground sites. With today's practices, this requires the costly excavation and stabilization of large rooms in mines. In this paper, we propose utilizing the caverns created by the solution mining of salt. The challenge is that such caverns must be filled with pressurized fluid and do not admit human access. We sketch some possible methods of installing familiar detector technologies in a salt cavern under these constraints. Some of the detectors discussed are also suitable for deep-sea experiments, discussed briefly. These sketches appear challenging but feasible, and appear to force few major compromises on detector capabilities. This scheme offers avenues for enormous cost savings on future detector megaprojects.

physics.ins-det↗

arXiv2014

Even-odd effects and Coulomb effects on minimal excitation energy of fragments from low energy fission

This work is focused on even-odd effects on the minimal total fragment excitation energy in thermal neutron induced fission of 233U and 235U as well as in spontaneous fission of 252Cf. In a scission model, taking into account the fragment deformation properties and Coulomb interaction between fragments, the expression of the difference between Q-values referred to even/even and odd/odd charge splits, respectively, on the corresponding difference between the minimal total fragment excitation energy is studied.

nucl-ex↗

arXiv2014

A digital CDS technique and the performance testing

Readout noise is a critical parameter for characterizing the performance of charge-coupled devices (CCDs), which can be greatly reduced by the correlated double sampling (CDS) circuit. However, conventional CDS circuit inevitably introduces new noises since it consists of several active analog components such as operational amplifiers. This paper proposes a digital CDS circuit technique, which transforms the pre-amplified CCD signal into a train of digital presentations by a high-speed data acquisition card directly without the noisy CDS circuit first, then implement the digital CDS algorithm through numerical method. The readout noise of 3.3 e$^{-}$ and the energy resolution of 121 eV@5.9keV can be achieved via the digital CDS technique.

physics.ins-det↗

arXiv2014

Proton and Neutron Momentum Distributions in A = 3 Asymmetric Nuclei

A proposal approved by the Jefferson Lab (JLab) PAC to study the proton-to-neutron momentum distribution ratio in A=3 nuclei via (e,e'p) scattering off 3He and 3H mirror nuclei. The experiment will measure the 3H(e,e'p) and 3He(e,e'p) cross-sections and cross-section ratios at Q2 = 2 and xB>1 kinematics, over a missing momentum range of 0 - 450 MeV/c. The experiment was approved in 2014 at part of the JLab Hall-A Tritium run period for a total run time of 12 days.

nucl-ex↗

arXiv2014

Beamline Instrumentation for Future Parity-Violation Experiments

The parity-violating electron scattering community has made tremendous progress over the last twenty five years in their ability to measure tiny asymmetries of order 100 parts per billion (ppb) with beam-related corrections and systematic errors of a few ppb. Future experiments are planned for about an order of magnitude smaller asymmetries and with higher rates in the detectors. These new experiments pose new challenges for the beam instrumentation and for the strategy for setting up the beam. In this contribution to PAVI14 I discuss several of these challenges and demands, with a focus on developments at Jefferson Lab.

nucl-ex↗

arXiv2014

High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride

In the course of investigations of thermal neutron detection based on mixtures of $^{10}$BF$_3$ with other gases, knowledge was required of the photoabsorption cross sections of $^{10}$BF$_3$ for wavelengths between 135 and 205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements reported in this communication. The measurements were made at the SURF III synchrotron radiation facility at the National Institute of Standards and Technology. The measured absorption cross sections vary from 10$^{-20}$ cm$^2$ at 135 nm to less than 10$^{-21}$ cm$^2$ in the region from 165 to 205 nm. Three previously unreported absorption features with resolvable structure were found in the regions 135 to 145 nm, 150 to 165 nm and 190 to 205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise from symmetry-changing adiabatic transitions.

physics.atom-ph↗

arXiv2014

Determination of the Free Neutron Lifetime

We present the status of current US experimental efforts to measure the lifetime of the free neutron by the "beam" and "bottle" methods. BBN nucleosynthesis models require accurate measurements with 1 second uncertainties, which are currently feasible. For tests of physics beyond the standard model, future efforts will need to achieve uncertainties well below 1 second. We outline paths achieve both.

nucl-ex↗

arXiv2014

Baseline LHC machine parameters and configuration of the 2015 proton run

This paper shows the baseline LHC machine parameters for the 2015 start-up. Many systems have been upgraded during LS1 and in 2015 the LHC will operate at a higher energy than before and with a tighter filling scheme. Therefore, the 2015 commissioning phase risks to be less smooth than in 2012. The proposed starting configuration puts the focus on feasibility rather than peak performance and includes margins for operational uncertainties. Instead, once beam experience and a better machine knowledge has been obtained, a push in $β^*$ and performance can be envisaged. In this paper, the focus is on collimation settings and reach in $β^*$---other parameters are covered in greater depth by other papers in these proceedings.

physics.acc-ph↗

arXiv2014

Estimate of cold nuclear matter effects on bottom production in d+Au collisions at $\sqrt{s_{NN}} = 200$ GeV

We investigate modification of the bottom quark production due to cold nuclear matter effects (CNM) at mid-rapidity in d+Au collisions at $\sqrt{s_{NN}} = 200$ GeV at RHIC. Our results indicate that bottom production is not suppressed due to CNM effects in those collisions. We also found that shadowing and initial $k_T$ breadboarding for charm quarks explains at low $p_T$ ($p_T < 3$ GeV/c) the enhancement of heavy flavor decay electron yield in d+Au collisions at $\sqrt{s_{NN}} = 200$ GeV compared to p+p.

nucl-ex↗

arXiv2014

Deuteron Electro-Disintegration at Very High Missing Momenta

We propose to measure the D(e,e'p) cross section at $Q^2 = 4.25$ (GeV/c)$^2$ and $x_{bj} = 1.35$ for missing momenta ranging from $p_m = 0.5$ GeV/c to $p_m = 1.0$ GeV/c expanding the range of missing momenta explored in the Hall A experiment (E01-020). At these energy and momentum transfers, calculations based on the eikonal approximation have been shown to be valid and recent experiments indicated that final state interactions are relatively small and possibly independent of missing momenta. This experiment will provide for the first time data in this kinematic regime which are of fundamental importance to the study of short range correlations and high density fluctuations in nuclei. The proposed experiment could serve as a commissioning experiment of the new SHMS together with the HMS in Hall C. A total beam time of 21 days is requested.

nucl-ex↗

arXiv2014

Neutron stars with Hyperons in Dirac-Brueckner-Hartree-Fock approach

Using the Dirac-Brueckner-Hartree-Fock (DBHF) approach including the hyperon degrees of freedom, we investigate the properties of neutron-star matter. To handle the hyperons in matter, we first examine the importance of the space part of baryon self-energies at high densities, and secondly study the effect of negative-energy states of baryons, which can provide an unambiguous relationship between the in-medium reaction matrices for baryon-baryon scattering and the baryon self-energies. We solve the coupled, Bethe-Salpeter equations in the nuclear-matter rest frame by using the Bonn potentials. We assume that eight kinds of nonstrange and strange mesons ($σ,\,δ,\,ω,\,ρ,\,η,\,π,\,K,\,K^{\ast}$) take part in the interactions between two baryons. Then, we calculate the baryon self-energies, the energy density and pressure of matter. The present calculation provides a hard equation of state in neutron-star matter at high densities, which is generated by the effect of Pauli exclusion, the short-range correlations between two baryons, etc. We finally predict the maximum neutron-star mass of $2.02\,M_{\odot}$, which is consistent with both the recently observed masses, $1.97\pm0.04M_{\odot}$ (J1614-2230) and $2.01\pm0.04M_{\odot}$ (J0348+0432).

nucl-th↗