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The recent successful detection of gravitational waves has been a century long Odyssey involvinga remarkable experiment and an elegant theory. In the latter aspect, it was made possible by a critical understanding of physical effects of gravitational waves and an improved understanding of the problem of two body motion in general relativity. This talk is a personal broad brush overview of how an unforgiving experiment drove an exquisite theory to create a sophisticated data analysis infrastructure to detect gravitational waves and to decipher their properties.

The Cryogenic Storage Ring (CSR) [1] located at Max-Planck-Institut für Kernphysik in Heidelberg,Germany is an ideal experimental setup to perform collision studies of photons and cold electrons as well neutrals with the stored molecular ions of kinetic energies between 20-300 keV. The circumference of the ring is 35 m and being fully electrostatic, it has no mass limit for stored ions. The cryogenic temperature of about 6 K offers unique storage capabilities in extremely high vacuum conditions of below 140 rest-gas particles per cm³ and almost vanishing blackbody radiation. An electron cooler(ecool) is installed in one straight section of the CSR which uses a photocathode to produce cold electrons. These cold electrons can further reduce the momentum spread of the stored ion beam upon interaction. A tunable optical parametric oscillator (OPO) laser system in the same section allows photon interaction studies from the ultraviolet (225 nm) to the infrared (2600 nm) regime. The CSR is equipped with two independent ion source platforms, which can deliver ions up to an energy of 60 and 300 keV per charge state, respectively. The low energy platform can be used to produce neutral beams by photodetachment of the negative ions. Whereas the 300 kV platform presently contains a metal ion sputter source, a Penning source and an electron cyclotron resonance source; extension by a laser vaporization and an electrospray ionization ion source is in progress. The entire facility enables to perform photodissociation, electron-ion recombination, and ion-atom interaction studies with ro-vibrationally cooled stored positive and negative ions as well as clusters and highly charged ions. Further experiments aim to study decay rates of metastable ions and radiative lifetimes. The first experimental results,machine characteristics as well as future experimental possibilities of this unique infrastructure will be discussed [2, 3].

References
[1] R. von Hahn, et al., Rev. Sci. Instrum. 87, 063115 (2016).
[2] A. O’ Connor, et al., Phys. Rev. Lett. 116, 113002 (2016).
[3] C. Meyer, et al., Phys. Rev. Lett. 119, 023202 (2017).

Abstract

The latest results of searches for exotic new physics from the CMS collaboration will be presented. The primary focus will be the searches of new particles decaying to leptons, including hadronically decaying tau leptons. Experimental signatures involving leptons are one of the cleanest probes of new physics at the LHC. These searches are based on proton-proton collision data at the LHC. In this talk, the status of data scouting will also be presented. CMS collaboration introduced the concept of data scouting as an alternative strategy to normal data-taking technique, allowing to take data that otherwise would be rejected by the trigger filters. This special data flow, based on event-size reduction rather than event filtering, is considered as a coherent discovery tool, and will be reviewed in this talk.

Abstract

Spin Hall Effect (SHE) and its inverse enables generation, manipulation and detection of pure spin current [1,2] in heavy metal thin films. The most common heavy metal that is heavily investigated is Pt. The β-phase of Ta and W offer higher spin Hall angle [3, 4] compared to Pt. However, there is significant variation in the values of spin Hall angle reported in the literature for both Ta and W. In this work, we explore the electrical and optical detection of spin currents of sputtered Ta thin films using Spin torque ferromagnetic resonance (STFMR), inverse spin Hall effect (ISHE) and magneto-optical Kerr (MOKE) measurements. In STFMR measurement, we show an anti-damping spin-orbit torque in epitaxial-Py/β-Ta that leads to nearly 30 % modulation of the effective Gilbert damping constant. The observed torque cannot be explained using the spin Hall effect and may arise from the interface or the crystalline structure of Py thin films [5]. We demonstrate a strong correlation of measured ISHE voltage with crystalline phase of Ta thin films and found a large spin Hall angle for a mixed crystalline phase of Ta.

We optically detect spin accumulation due to the spin Hall effect in single layer Ta films by applying a square wave current and using Fourier analysis in a MOKE setup that uses spatially modulated incident light. We show that there exists a threshold current density (Jth) above which spin current can be detected via the optical technique. Jth, which is a measure of spin current efficiency, is found to be the lowest in the mixed phase of Ta and is strongly correlated with the crystalline phase of Ta [6].

References

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• S. O. Valenzuela and M. Tinkham, Nature 442, 176–179 (2006).
• L. Q. Liu et al., Science 336, 555–558 (2012).
• C. F. Pai et al., Appl. Phys. Lett. 101, 122404 (2012).