2017 Fall Seminar List

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Fall 2017 LeCosPA Cosmology and Particle Astrophysics Seminars

Location : Room 812, Astro-Math Building, NTU
Time : 11:00-12:00, Monday
Time for ASIAA/LeCosPA Joint Seminar : 14:20-15:20 on specific Thursdays
Organizers :Dr. Nugier, Fabien & Dr. TC Liu

Date Name Title Affiliation File
Sep./11
Dr. Ken Chen
Physics of the first Stars, Supernovae, and Galaxies
One of the paramount problems in modern cosmology is to elucidate how the first generation of luminous objects, stars, supernovae, accreting black holes, and galaxies, shaped the early universe at the end of the cosmic dark ages. According to the modern theory of cosmological structure formation, the hierarchical assembly of dark matter halos provided the gravitational potential wells that allowed gas to form stars and galaxies inside them. Modern large telescopes have pushed the detection of galaxies up to a redshift of z ~ 10. However, models of the first luminous objects still require considerable effort to reach the level of sophistication necessary for meaningful predictions, Due to the complexity of involved physical phenomena, this physical understanding may only come by the proper use of numerical simulations. Therefore, I have used state-of-the-art simulations on some of largest supercomputers to study these objects. In my talk, I will discuss the possible physics behind the formation of these first luminous objects by presenting the results from our simulations. I will also give possible observational signatures of the cosmic dawn that will be the prime targets for the future telescopes such as the James Webb Space Telescope (JWST).
ASIAA
Sep./18
Dr. YoungMin Yook
Search for the Leptonic B Meson Decays at the Belle Experiment
A search for the purely leptonic $B$ meson decays $B^+\to\ell^+\nu_\ell$, where $\ell=e,~\mu$, using the full $\Upsilon(4S)$ data sample of $772\times 10^6~B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider and a sensitivity study of the lepton flavor violating leptonic $B$ meson decay $B^0\to\ell^\pm\tau^\mp$ are presented. In the studies, one of the $B$ mesons from $\Upsilon(4S)\to B\bar{B}$ decay is fully reconstructed in a hadronic mode, while the recoiling side is analyzed for the signal decay.


In the search for the $B^+\to\ell^+\nu_\ell$ decays no evidence of the signal in both decay modes is found. Upper limits of the corresponding branching fractions are determined as ${\cal B}(B^+\to e^+\nu_e)<3.5\times 10^{-6}$ and ${\cal B}(B^+\to \mu^+\nu_\nu)<2.7\times 10^{-6}$ at 90\% confidence level.

Useful variables that can be utilized in the $B^0\to\ell^\pm\tau^\mp$ decays as well as the performance of analysis estimated by an MC study is also presented. Compared to the most recent and stringent result, also performed at the $B$-factory experiment using hadronic tagging, approximately 10\%~(50\%) improvement in the signal efficiency is expected in the $B^0\to e^\pm\tau^\mp$~($B^0\to \mu^\pm\tau^\mp$) mode while reducing the background events to half.

Yonsei Univ.
Sep./25
Prof. Yi-Zen Chu
Cosmological Gravitational Waves: Causal Structure And Memories
[ Exceptional change of time: 10.30am - 11.30am ]
Despite being associated with particles of zero rest mass, electromagnetic and gravitational waves do not travel solely on the null cone in generic curved spacetimes. (That is, light does not always propagate on the light cone.) This inside-the-null-cone propagation of waves is known as the tail effect, and finding novel ways of understanding it in the strong field regime near a black hole may find applications for modeling the gravitational signals sought after by next-generation space-based detectors such as LISA.

Motivated by these considerations -- and as a first step -- I have been exploring techniques to understand the causal structure of scalar, electromagnetic and gravitational waves in cosmological spacetimes. I will describe my efforts to date, which include how the gravitational wave memory effects in 4D asymptotically flat spacetime generalize to the cosmological case.

NCU
Oct./02
Prof. Stathes Paganis
New Higgs results from LHC with implications to Cosmology.
The ATLAS and CMS experiments are currently releasing new results

obtained with the full ~36 fb^-1 luminosity 2016 dataset. Higgs related searches are relevant to cosmology and particle astrophysics, since they involve searches for Dark Matter, extra dimensions, studies of the Higgs potential and more. The goal of this talk is to summarize these results to a cosmology audience and give some update on the Taiwanese involvement in improving these searches.

NTU, LeCosPA
Oct./16
Dr. Rio Saitou
TBA
TBA
LeCosPA
Oct./23
Dr. Meng-Ru Wu
TBA
TBA
IoP, SINICA
Oct./30
Dr. Yuichi Higuchi
TBA
TBA
ASIAA
Nov./06
Dr. KunXian Huang
T2K
NTU


Nov./13
Dr. Jiro Matsumoto
TBA
TBA
LeCosPA
Nov./22


Nov./27
LeCosPA 3rd Symposium LeCosPA
Dec./04


Dec./11


Dec./18
Prof. Guey-Lin Lin
TBA
TBA
IoP, NCTU


Dec./25



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