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<div style="font-family:"Segoe UI",Helvetica,Arial,sans-serif"><span id="docs-internal-guid-86d1851e-9600-8d8e-733d-c5fa57d08efb"><span id="docs-internal-guid-9e838874-b9fd-c26f-7292-368ffed344e3">
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<div style="text-align:center"><span style="font-size:11pt; font-family:Cambria; background-color:rgb(255,255,255); vertical-align:baseline; white-space:pre-wrap"><span id="docs-internal-guid-748f50ce-f689-54d2-9b41-5a3c77a9e486"><span id="docs-internal-guid-44741882-f788-0e32-c8e8-2b168c3681ef"><span id="docs-internal-guid-d5bed97d-3f42-6ae7-0034-104ccf7b3897">
<p dir="ltr" style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="font-size: 28pt; color: rgb(192, 0, 0); background-color: transparent; font-weight: 700; vertical-align: baseline;">Spring 2018 Colloquium</span></p>
<p dir="ltr" style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="font-size: 16pt; background-color: transparent; font-weight: 700; vertical-align: baseline;">Department of Physics & Astronomy, TAMU-Commerce</span></p>
<p dir="ltr" style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="font-size: 16pt; color: rgb(192, 0, 0); background-color: transparent; font-weight: 700; vertical-align: baseline;">Mar 22, Thursday, 4-5 PM in Science Building 127</span></p>
<p dir="ltr" style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="font-size: 14pt; background-color: transparent; vertical-align: baseline;">(coffee and cookies will be served at 3:50 PM)</span></p>
<p dir="ltr" style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="font-size: 18pt; color: rgb(0, 176, 80); background-color: transparent; font-weight: 700; vertical-align: baseline;">Astrophysics, Particle physics</span></p>
<p dir="ltr" style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="font-size: 18pt; color: rgb(0, 0, 255); background-color: transparent; font-weight: 700; vertical-align: baseline;">Astrophysical Neutrinos:
</span><span style="font-size: 18pt; color: rgb(0, 0, 255); background-color: transparent; font-weight: 700; vertical-align: baseline;"><br class="kix-line-break">
</span><span style="font-size: 18pt; color: rgb(0, 0, 255); background-color: transparent; font-weight: 700; vertical-align: baseline;">What do they tell us about cosmic accelerators?</span><span style="font-size: 18pt; color: rgb(0, 0, 255); background-color: transparent; font-weight: 700; vertical-align: baseline;"><br class="kix-line-break">
</span><span style="font-size: 14pt; background-color: transparent; font-weight: 700; vertical-align: baseline;">Dr. Spencer Klein</span></p>
<p dir="ltr" style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="font-size: 14pt; background-color: transparent; font-weight: 700; vertical-align: baseline;">Lawrence Berkeley National Laboratory & Univ. of California at Berkeley</span></p>
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<p dir="ltr" style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="font-size: 14pt; background-color: transparent; font-weight: 700; vertical-align: baseline;"></span><img src="https://lh3.googleusercontent.com/jzwdsLW8OFMq_CVsrMbCdo0o7ZFhOqdxASVks9W2e1m06BpR8O-c1zbB623ti6qPk4hPQi52-K-QEWMNI4YoihhzDTA7UzhiVASP3e41mj3yteraNntXjcC-6SB9It7CzzgHTgrS" width="122" height="146" style="border: none; transform: rotate(0.00rad); -webkit-transform: rotate(0.00rad);"></p>
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<span style="font-size: 11pt; vertical-align: baseline;">Dr. Klein earned his BA in 1982 from the University of California, San Diego, and his PhD from Stanford University in 1988 for dissertation work on 29 GeV e^+e^- collisions. From there, he moved into
astroparticle physics, with postdocs at Boston University, on MACRO [Monopole, Astrophysics and Cosmic-Ray Observatory] and UC Santa Cruz on Cygnus, Milagro and the Landau-Pomeranchuk Effect. In 1994, he moved to Lawrence Berkeley National Lab, to work on
heavy-ion collisions with the STAR detector at RHIC, where he is currently a senior scientist; he also has an appointment as a research physicist at UC Berkeley. His current interests include neutrino astroparticle physics with IceCube and ARIANNA, and ultra-peripheral
collisions with STAR and ALICE. He has a blog, </span><a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__antarcticaneutrinos.blogspot.com_&d=DwMD-g&c=oqyuZuih6ykib6aKiBq22_bich4AVfYGoLertJN0bEc&r=oW0cJCgG9kL3hewogz7V9J0OTS6PpWhN7lR7LkypiUg&m=bWkJAZEO0ukALOJYk3Regz6yFroh-BPacNvZW1fm9Wk&s=JyeH7OJEXwl4lcSeDtFx7TAl8rIJsop9EAee699DLVw&e=" style="text-decoration-line: none;"><span style="font-size: 11pt; color: rgb(17, 85, 204); text-decoration-line: underline; vertical-align: baseline;">http://antarcticaneutrinos.blogspot.com/</span></a><span style="font-size: 11pt; vertical-align: baseline;">.
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<p dir="ltr" style="line-height:1.38;margin-top:0pt;margin-bottom:4pt;"><span style="font-size: 12pt; background-color: transparent; font-weight: 700; vertical-align: baseline;">Abstract</span></p>
<p dir="ltr" style="line-height:1.38;margin-top:0pt;margin-bottom:0pt;text-align: justify;">
<span style="font-size: 11pt; vertical-align: baseline;">The existence of cosmic-rays with energies well above 10</span><span style="font-size: 6.6pt; vertical-align: super;">^20</span><span style="font-size: 11pt; vertical-align: baseline;"> electron volts
(16 Joules) is a long-standing mystery; producing them requires either enormously powerful astrophysical accelerators, or something exotic. One way to shed light on cosmic-rays accelerators is to search for their signal in another channel - neutrinos! The
IceCube detector has observed a diffuse flux of astrophysical neutrinos, extending to energies well above 1 PeV (10</span><span style="font-size: 6.6pt; vertical-align: super;">^15</span><span style="font-size: 11pt; vertical-align: baseline;"> eV). This
flux has been observed by multiple analyses using independent datasets, with high significance. This flux is near the maximum predicted ("Waxman-Bahcall bound") from astrophysical accelerators. Most popular source models, involving gamma-ray bursts, active
galactic nuclei (galactic centers containing supermassive black holes), and even star-forming galaxies are disfavored to varying degrees. In this talk, I will discuss the IceCube results in the context of cosmic-ray physics and give the status of different
classes of source models. I will conclude by discussing some possible future experiments.
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