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nucl-ex Update: 2010-09-07

SciTes
0
1009.0799 [abs pdf who comments(0)]
Title: Measuring the muon's anomalous magnetic moment to 0.14 ppm
Authors: Frederick Gray, for the New

The anomalous magnetic moment (g-2) of the muon was measured with a precision of 0.54 ppm in Experiment 821 at Brookhaven National Laboratory. A difference of 3.2 standard deviations between this experimental value and the prediction of the Standard Model has persisted since 2004; in spite of considerable experimental and theoretical effort, there is no consistent explanation for this difference. This comparison hints at physics beyond the Standard Model, but it also imposes strong constraints on those possibilities, which include supersymmetry and extra dimensions. The collaboration is preparing to relocate the experiment to Fermilab to continue towards a proposed precision of 0.14 ppm. This will require 20 times more recorded decays than in the previous measurement, with corresponding improvements in the systematic uncertainties. We describe the theoretical developments and the experimental upgrades that provide a compelling motivation for the new measurement.

SciTes
0
1009.0898 [abs pdf who comments(0)]
Title: Radioactive contamination of ZnWO4 crystal scintillators
Authors: P. Belli, R. Bernabei, F. Cappella, R. Cerulli, F. A. Danevich, A. M. Dubovik, S. d'Angelo, E. N. Galashov, B. V. Grinyov, A. Incicchitti, V. V. Kobychev, M. Laubenstein, L. L. Nagornaya, F. Nozzoli, D. V. Poda, R. B. Podviyanuk, O. G. Polischuk, D. Prosperi, V. N. Shlegel, V. I. Tretyak, I. A. Tupitsyna, Ya. V. Vasiliev, Yu. Ya. Vostretsov

The radioactive contamination of ZnWO4 crystal scintillators has been measured deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN in Italy with a total exposure 3197 kg x h. Monte Carlo simulation, time-amplitude and pulse-shape analyses of the data have been applied to estimate the radioactive contamination of the ZnWO4 samples. One of the ZnWO4 crystals has also been tested by ultra-low background gamma spectrometry. The radioactive contaminations of the ZnWO4 samples do not exceed 0.002 – 0.8 mBq/kg (depending on the radionuclide), the total alpha activity is in the range: 0.2 - 2 mBq/kg. Particular radioactivity, beta active 65Zn and alpha active 180W, has been detected. The effect of the re-crystallization on the radiopurity of the ZnWO4 crystal has been studied. The radioactive contamination of samples of the ceramic details of the set-ups used in the crystals growth has been checked by low background gamma spectrometry. A project scheme on further improvement of the radiopurity level of the ZnWO4 crystal scintillators is briefly addressed.

SciTes
0
1009.0946 [abs pdf who comments(0)]
Title: Measurement of the Lambda(1405) in proton proton reactions with HADES
Authors: Johannes Siebenson, Laura Fabbietti, Alexander Schmah, Eliane Epple, for the HADES Collaboration

We present an analysis of the Lambda(1405) resonance in p+p reactions at a kinetic beam energy of 3.5 GeV, measured by the High Acceptance Di-Electron Spectrometer (HADES). The resonance is reconstructed in the two charged decay channels Sigma^(+/-) pi^(-/+), with help of a kinematic refit, which improves the mass resolution. The high misidentification of pions and protons as kaons required the development of a sophisticated sideband analysis, which can describe the misidentification background quite well.

SciTes
0
1009.1000 [abs pdf who comments(0)]
Title: Electron-capture supernovae as the origin of elements beyond iron
Authors: Shinya Wanajo, Hans-Thomas Janka, Bernhard Mueller

We examine electron-capture supernovae (ECSNe) as sources of elements heavier than iron in the solar system and in Galactic halo stars. Nucleosynthesis calculations are performed on the basis of thermodynamic histories of mass elements from a fully self-consistent, two-dimensional (2D) hydrodynamic explosion model of an ECSN. We find that neutron-rich convective lumps with an electron fraction down to Ye,min=0.40, which are absent in the one-dimensional (1D) counterpart, allow for interesting production of elements between the iron group and N=50 nuclei (from Zn to Zr, with little Ga) in nuclear statistical equilibrium and by the alpha-process. Our models yield very good agreement with the Ge, Sr, Y, and Zr abundances of r-process deficient Galactic halo stars and constrain the occurrence of ECSNe to ~4% of all stellar core-collapse events. If tiny amounts of additional material with slightly lower Ye,min down to ~0.30-0.35 were also ejected - which presently cannot be excluded because of the limitations of resolution and two-dimensionality of the model -, a weak r-process can yield elements beyond N=50 up to Pd, Ag, and Cd as observed in the r-process deficient stars.

SciTes
0
1009.1035 [abs pdf who comments(0)]
Title: NA61/SHINE ion program
Authors: Maja Mackowiak for the NA61 Collaboration

The Super Proton Synchrotron (SPS) at CERN covers one of the most interesting regions of the phase diagram (T - \mu_{B}) of strongly interacting matter. The study of central Pb+Pb collisions by NA49 indicate that the threshold for deconfinement is reached already at the low SPS energies. Theoretical considerations predict a critical point of strongly interacting matter at energies accessible at the SPS. The NA61/SHINE experiment, a successor of the NA49 project, will study hadron production in p+p, p+A, h+A, and A+A reactions at various energies. The broad physics program includes the investigation of the properties of strongly interacting matter, as well as precision measurements of hadron spectra for the T2K neutrino experiment and for the Pierre Auger Observatory and KASCADE cosmic-ray projects. The main physics goals of the NA61/SHINE ion program are to study the properties of the onset of deconfinement at low SPS energies and to find signatures of the critical point of strongly interacting matter. To achieve these goals a broad range in the (T - \mu_{B}) phase diagram will be covered by performing an energy (10A-158A GeV/c) and system size (p+p, B+C, Ar+Ca, Xe+La) scan. The first data for this 2-D scan were taken in 2009, i.e. p+p interactions at 20, 30, 40, 80, 158 GeV/c beam energy. This contribution will summarize physics arguments for the NA61/SHINE ion program, show the detector performance and present the current status of the experiment and plans for the next years.

SciTes
0
1003.2834 [abs pdf who comments(0)] [CROSS LISTED]
Title: Quartet of spin-3/2 baryons in chiral multiplet $(1, 1/2) \oplus (1/2, 1) $ with mirror assignment
Authors: Keitaro Nagata

We study the possible existence of chiral partners in the spin-$\thalf$ sector of the baryon spectrum. We consider a quartet scheme where four spin-3/2 baryons, $P_{33}$, $D_{33}$, $D_{13}$ and $P_{13}$, group into higher-dimensional chiral multiplets $(1, \half)\oplus (\half,1)$ with a mirror assignment. With an effective $SU(2)_R\times SU(2)_L$ Lagrangian, we derive constraints imposed by chiral symmetry together with the mirror assignment on the masses and coupling constants of the quartet. Using those constraints, we try to find a set of baryons suitable for the chiral quartet. It turns out that three cases reasonably agree with the features of the quartet: (1) ($\Delta(1232)$, $\Delta(1700)$, N(1520), $N(1720))$, (2) ($\Delta(1232)$, $\Delta(1940)$, N(1520), $N(1720))$, (3) ($\Delta(1600)$, $\Delta(1940)$, N(1520$, $N(1720))$. We discuss the features of these cases with careful attention to how they are distinguished. We also study four spin-$\thalf$ baryons that are approximately degenerate, ($\Delta(1920)$, $\Delta(1940)$, N(1900), N(2080)), using the quartet scheme.

SciTes
0
1005.2957 [abs pdf who comments(0)] [CROSS LISTED]
Title: Associated strangeness production in the pp to pK^+K^-p and pp to pK^+ pi^0 Sigma^0 reactions
Authors: Ju-Jun Xie, Colin Wilkin

The total and differential cross sections for associated strangeness production in the $pp \to pK^+K^-p$ and $pp \to pK^+\pi^0\Sigma^0$ reactions have been studied in a unified approach using an effective Lagrangian model. It is assumed that both the $K^-p$ and $\pi^0\Sigma^0$ final states originate from the decay of the $\Lambda(1405)$ resonance which was formed in the production chain $pp\to p(N^*(1535)\to K^+\Lambda(1405))$. The available experimental data are well reproduced, especially the ratio of the two total cross sections, which is much less sensitive to the particular model of the entrance channel. The significant coupling of the $N^*(1535)$ resonance to $\Lambda(1405) K$ is further evidence for large $s \bar{s}$ components in the quark wave function of the $N^*(1535)$ resonance.

2010-09-06 and older
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Recent Comments

1002.3824 wilson : In this paper Sedrakyan and Chubukov have finally resolved the long-standing issue about the origin of the pseudogap in cuprates. This study...

1007.1749 dabacon : Figures 3 and 4 are...interesting?

1005.5173 renner : To clarify in response to the above comment, our main result is that quantum theory cannot be *extended*. We consider an extension to a the...

1005.5173 peaches : I'm not sure that it's fair to say that this is is an extension of Bell's result in the general case because the main theorem relies on the ...

1005.4932 ayvlasov : I am not quite realizing, if it is necessary to make some comments, because most arguments already have been raised by few different people ...

1004.0411 sattath : Hi,

First thing: it's a very interesting and beautiful result.

Unfortunately, I didn't fully understand the soundness ...

1005.0411 plasky : Dear Dan,

Thank you for the nice resource paper on various mass profiles. Last year Chris Fluke and I published a paper explorin...

1004.5186 and78 : Nice results! It is not your goal but it'd be important to know how well it behaves on social networks.

1004.1645 ayvlasov : I think, Phys. Rev. A 63, 054302 (arXiv:quant-ph/0010071)
may be interesting ...

1005.0411 Zhao : Dear Dan,

Your two new paper on Astroph look very nice and I wish a recent paper of us be of interest to you.

We ...

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