Experimental Particle and Astro-Particle Physics Seminar

29 January

13:00

Y27 H 37

(note unusual time and location)

Yasmine Amhis

(Centre National de la Recherche Scientifique)

About the universality (or not) of loop induced beauty decays. 

The coupling of the electroweak gauge bosons of the Standard Model  to leptons is lepton flavour universal. Extensions of the Standard model do not necessarily have this property. Rare decays of heavy flavour are heavily suppressed in the Standard Model and new particles can give sizeable contributions to these processes, thus their precise study allows for sensitive tests of lepton flavour universality. Of particular interest are rare b->sll decays that are readily accessible at the LHCb experiment. Recent results from LHCb on lepton flavour universality in rare b->sll decays are discussed.

17 February

24 February

2 March

9 March

Differential Jet Production Cross Section Measurements at CMS

I begin with the motivation for studying jet mass in terms of understanding pQCD and decreasing uncertainties on future searches for new physics. I will then discuss our CMS dijet mass measurement as an introduction to my thesis research, the jet mass and dimensionless mass measurement with respect to transverse momentum in Z + jet events from the entire run 2 dataset of CMS.

16 March

23 March

30 March

6 April

13 April

Easter Monday

20 April

Sechseläuten

27 April
Remote

4 May

11 May
Remote

Pulsars, Jets & GRBs: Recent Highlights from the H.E.S.S. Gamma-ray Observatory

In the 15 years since its construction, the H.E.S.S. gamma-ray observatory has allowed the study of the VHE gamma-ray sky at resolutions and sensitivities which were never before possible. During this period H.E.S.S. has discovered a rich zoo of both galactic and extra galactic source classes, made measurements of the galactic cosmic ray spectrum and placed limits on fundamental physical processes. 

I will present a brief summary of the some of the highlights of the H.E.S.S. observational programme, concentrating on the study of transient sources which has been a strong focus of the H.E.S.S. telescopes in recent years. Most notably this lead to the detection of two gamma-ray bursts in the very high energy range, but also has placed limits on the gamma-ray emission for the numerous gravitational wave sources (including GW 170817), Fast Radio Bursts and neutrino source candidates. Finally I will detail the latest upgrades to H.E.S.S. and the plans for future operation. 

18 May
Remote

Rare, slow and special - Detecting the double-beta decays of Xe-124

The isotope ¹²⁴Xe is exceedingly rare and long-lived. Still, its slow double-beta decays could be a key to understanding the mass and nature of the neutrino as well as the dominance of matter over antimatter in the Universe. What makes ¹²⁴Xe special among double-beta emitters is the theoretical possibility of three different neutrinoless decay modes – either in a nuclear resonance, or involving the emission of one or two positrons. Together with the observation of neutrinoless double-beta decays in other isotopes, ¹²⁴Xe could also allow to disentangle the underlying decay mechanism. The talk will introduce the neutrinoless and two-neutrino decays of ¹²⁴Xe and discuss the detection prospects with upcoming experiments such as XENONnT, nEXO and DARWIN.

25 May

Remote

Low Gain Avalanche Diodes – Towards picosecond fast radiation hard fully segmented tracking?

The factor of 10 increase in LHC-Phase 2 instantaneous luminosity, results in a high multiplicity environment were vertex separation by means of position sensitive tracking becomes challenging. Addition of a < 60 psec timing layer, based on Low Gain Avalanche Diode technology, has been proposed by both CMS and ATLAS experiments in problematic regions to recover performance. By means of moderate intrinsic gain (~10), fast signals with high S/N are produced, providing a low-jitter and high charge approach. Main challenges include radiation hardness to fluences up to several times 10¹⁵ n_eq/cm², fine segmentation, increased geometric acceptance and stability – efficiency in a continuous operation environment. The state of the art is presented in all fronts and future research directions are discussed. Gallium and Carbon implants are explored for radiation resistance enhancement in combination with trenches and non-segmented gain layers towards a fill factor increase.