Faddeev calculation of pentaquark Θ+\Theta^+ in the Nambu-Jona-Lasinio model-based diquark picture

A Bethe-Salpeter-Faddeev (BSF) calculation is performed for the pentaquark $\Theta^+$ in the diquark picture of Jaffe and Wilczek in which $\Theta^+$ is a diquark-diquark-${\bar s}$ three-body system. Nambu-Jona-Lasinio (NJL) model is used to calculate the lowest order diagrams in the two-body scatterings of ${\bar s}D$ and $D D$. With the use of coupling constants determined from the meson sector, we find that ${\bar s}D$ interaction is attractive in s-wave while $DD$ interaction is repulsive in p-wave. With only the lowest three-body channel considered, we do not find a bound $\frac 12^+$ pentaquark state. Instead, a bound pentaquark $\Theta^+$ with $\frac 12^-$ is obtained with a unphysically strong vector mesonic coupling constants.Comment: 22 pages, 11 figures, accepted version in Phys. Rev. C. Summary of main changes/corrections: 1. "which only holds at tree level" below the eq. (23) is added. 2. In the last paragraph of p.23 we added a remark that the coupling constant obtained from Lambda mass is different from the estimate as obtained from the meson spectru

An extreme, blueshifted iron line profile in the Narrow Line Seyfert 1 PG 1402+261; an edge-on accretion disk or highly ionized absorption?

We report on a short XMM-Newton observation of the radio-quiet Narrow Line Seyfert 1 PG 1402+261. The EPIC X-ray spectrum of PG 1402+261 shows a strong excess of counts between 6-9 keV in the rest frame. This feature can be modeled by an unusually strong (equivalent width 2 keV) and very broad (FWHM velocity of 110000 km/s) iron K-shell emission line. The line centroid energy at 7.3 keV appears blue-shifted with respect to the iron Kalpha emission band between 6.4-6.97 keV, while the blue-wing of the line extends to 9 keV in the quasar rest frame. The line profile can be fitted by reflection from the inner accretion disk, but an inclination angle of >60 deg is required to model the extreme blue-wing of the line. Furthermore the extreme strength of the line requires a geometry whereby the hard X-ray emission from PG 1402+261 above 2 keV is dominated by the pure-reflection component from the disk, while little or none of the direct hard power-law is observed. Alternatively the spectrum above 2 keV may instead be explained by an ionized absorber, if the column density is sufficiently high (N_H > 3 x 10^23 cm^-2) and if the matter is ionized enough to produce a deep (tau~1) iron K-shell absorption edge at 9 keV. This absorber could originate in a large column density, high velocity outflow, perhaps similar to those which appear to be observed in several other high accretion rate AGN. Further observations, especially at higher spectral resolution, are required to distinguish between the accretion disk reflection or outflow scenarios.Comment: Accepted for publication in ApJ (18 pages, 5 figures, 1 table

X-ray Phase-Resolved Spectroscopy of PSRs B0531+21, B1509-58, and B0540-69 with RXTE

The Rossi X-ray Timing Explorer ({\sl RXTE}) has made hundreds of observations on three famous young pulsars (PSRs) B0531+21 (Crab), B1509-58, and B0540-69. Using the archive {\sl RXTE} data, we have studied the phase-resolved spectral properties of these pulsars in details. The variation of the X-ray spectrum with phase of PSR B0531+21 is confirmed here much more precisely and more details are revealed than the previous studies: the spectrum softens from the beginning of the first pulse, turns to harden right at the pulse peak and becomes the hardest at the bottom of the bridge, softens gradually until the second peak, and then softens rapidly. Different from the previous studies, we found that the spectrum of PSR B1509-58 is significantly harder in the center of the pulse, which is also in contrast to that of PSR B0531+21. The variation of the X-ray spectrum of PSR B0540-69 seems similar to that of PSR B1509-58, but with a lower significance. Using the about 10 years of data span, we also studied the real time evolution of the spectra of these pulsars, and no significant evolution has been detected. We have discussed about the constraints of these results on theoretical models of pulsar X-ray emission.Comment: 42 pages, 24 figure

Using Coded Excitation to maintain Signal to Noise for FMC+TFM on Attenuating Materials

Ultrasonic Non-Destructive Evaluation using Full Matrix Capture (FMC) and Total Focusing Method (TFM) is used for high resolution imaging as every pixel is in optimal focus. FMC excites one element in turn, so operates with lower transmitted energy compared to phased array beamforming. The energy at a reflector is further reduced by the broad directivity pattern of the single element. The large number of Tx/Rx A-scans that contribute to each pixel recover the Signal-to-Noise Ratio (SNR) in the final TFM image. Maintaining this in the presence of attenuating materials is a challenge because relevant information in each A-scan signal is buried in the thermal noise, and the TFM process assumes no quantization effects in the Analogue-to-Digital Converters (ADCs) in each receiver. In-process inspection during Additive Manufacturing (AM) requires ultrasonic array sensors that can tolerate high temperatures, scan over rough surfaces and leave no residue. Dry-coupled wheel probes are a solution, but the tire rubbers are often highly attenuating, causing a problem for FMC+TFM needed to adapt the focus through the rough surface. Common approaches to maintain the SNR are to drop the frequency or to average over multiple transmissions, but these compromise resolution and acquisition rate respectively. In this paper, the application of coded excitation to maintain the SNR in the presence of high signal attenuation is explored

Intentional weld defect process: From manufacturing by robotic welding machine to inspection using TFM phased array

Specimens with intentionally embedded weld defects or flaws can be employed for training, development and research into procedures for mechanical property evaluation and structural integrity assessment. It is critical that the artificial defects are a realistic representation of the flaws produced by welding. Cylindrical holes, which are usually machined after welding, are not realistic enough for our purposes as it is known that they are easier to detect than the naturally occurring imperfections and cracks. Furthermore, it is usually impractical to machine a defect in a location similar to where the real weld defects are found. For example, electro-discharge machining can produce a through hole (cylindrical reflector) which neither represents the weld porosity (spherical voids) nor the weld crack (planar thin voids). In this study, the aim is to embed reflectors inside the weld intentionally, and then locate them using ultrasonic phased array imaging. The specimen is an 8 mm thick 080A15 Bright Drawn Steel plate of length 300 mm. Tungsten rods (ø2.4-3.2 mm & length 20-25 mm) and tungsten carbide balls (ø4 mm) will be used to serve as reflectors simulating defects within the weld itself. This study is aligned to a larger research project investigating multi-layer metal NDE found in many multi-pass welding and wire arc additive manufacturing (WAAM) applications and as such, there is no joint preparation as the first layer is deposited over the plate surface directly and subsequent layers contribute to the specimen build profile, similar to the WAAM samples. A tungsten inert gas welding torch mounted on a KUKA robot is used to deposit four layers for each weld, with our process using nine passes for the first layer, down to six passes for the last layer. During this procedure, the tungsten artificial reflectors are embedded in the weld, between the existing layers. The sample is then inspected by a 10 MHz ultrasonic phased array in direct contact with the sample surface using both conventional and total focusing method (TFM) imaging techniques. A phased array aperture of 32 elements has been used. The phased array controller is FIToolbox (Diagnostic Sonar, UK). Firstly, a focused B-scan has been performed with a range of settings for the transmit focal depth. Secondly, a full-aperture TFM method has been processed. All the reflectors of interest were detected successfully using this combination of B-scan and TFM imaging approaches

High-temperature in-process inspection followed by 96-h robotic inspection of intentionally manufactured hydrogen crack in multi-pass robotic welding

This investigation introduces two new techniques to quantitatively address the challenging problem of understanding Hydrogen Induced Cracking (HIC) in welding processes. The first technique is a novel procedure to create a known and controlled HIC in a welded sample. The second is an in-process monitoring technique to measure the initial formation and subsequent growth of the HIC in a multi-pass weld whilst being compatible with the high temperatures associated with the welding process. The HIC was initiated using a localised quenching method of the weld and its character was verified using both macrograph and microscopic investigations. During HIC initiation and growth, the sample was monitored every 1–30 min for a total of 96 h using a custom non-destructive testing (NDT) system, mounted on a robot which ensured repeatable inspection positioning. Combining these techniques has therefore allowed for the first time, a detailed understanding of the evolution of HIC in a multi-pass welded sample. Our findings reveal that the HIC was initiated 43 min after the weld ended and that it then grew rapidly for about 15 min and continued growing at a slower rate for around 24 h. No significant growth was observed for the remaining 72 h of the experimental measurement

Continuous monitoring of an intentionally-manufactured crack using an automated welding and in-process inspection system

Automated weld deposition coupled with the real-time robotic Non-Destructive Evaluation (NDE) is used in this paper. For performance verification of the in-process inspection system, an intentionally embedded defect, a tungsten rod, is introduced into the multi-pass weld. A partially-filled groove (staircase) sample is also manufactured and ultrasonically tested to calibrate the real-time inspection implemented on all seven layers of the weld which are deposited progressively. The tungsten rod is successfully detected in the real-time NDE of the deposited position. The same robotic inspection system was then used to continuously monitor an intentionally-manufactured crack for 20 h. The crack was initiated 22 min after the weld ended and it grew quickly within the next 1.5 h. The crack growth stopped approximately after 2 h and no considerable change in the reflection signal was detected for the next 18 h of monitoring

Nanofilm Allotrope and Phase Transformation of Ultrathin Bi Film on Si(111)7X7

金沢大学理学部Nanofilm allotrope and phase transformation of ultrathin Bi film on Si(111)-7 × 7 were analyzed using scanning tunneling microscopy and electron diffraction experiments. It was observed that this pseudocubic {012}-oriented allotrope is stable up to four atomic layers at room temperature. The entire volume of the film started to transform into a bulk single-crystal (001) phase, as the bulk contribution in the cohesion became dominant, above the critical thickness. It was proposed that the allotrope consists of black phosphorus-like puckered layers stabilized by saturating all the pz dangling bonds in the film, based on ab initio calculations