# First Young Scientists Forum of the SFB TRR 257

Europe/Berlin
Remotely

#### Remotely

Description

This is the event page of the First Young Scientists Forum
of the Collaborative Research Center TRR 257.

Dates: June 09th, 17th and 23th.
Time:  02pm - 4:30pm.

The Young Scientists Forum is a series of remote seminars given by Ph.D. students and young Postocs from Aachen, Heidelberg, Karlsruhe and Siegen. It features short (12+3) presentations, preparing the speakers to talk about their research in front of a large audience.

How2Join?

Location of the Event:
https://teaching.particle.kit.edu/b/mar-f4t-u4w
Access Code: <cencored (read announcement mail)>
Change to slide-view: click on lower-right icon once the meeting has started (we will start the meeting about 10 min. before the session starts)

Technical information for all participants:

The seminar will be held on bigbluebutton (https://teaching.particle.kit.edu/b/mar-f4t-u4w).
Requirements for you from their FAQs are:

For bandwidth, we recommend 1Mbits download and 0.5 Mbits upload speed. Users can test their actual bandwidth using speedtest.net.
For hardware, we recommend a dual-core CPU with at least 2G of memory. We recommend any operating system capable of running the latest versions of Google Chrome and Mozilla FireFox.
For browser, we recommend running either FireFox or Chrome. Why? Both browsers provide excellent support for web real-time communications (WebRTC). Safari, IE, and Edge will work as well, but FireFox and Chrome will deliver better audio in lower bandwidth conditions.
In short, if the user is having any problems (such as audio is garbled or they are periodically getting disconnected), we recommend trying either FireFox or Chrome.

Please keep yourself muted. There are ~3 minutes reserved for questions after each talk.
If you want to ask a question unmute and speak or ask/announce your question in the public chat.

Technical information for all speakers:

When joining the Event, please enter your full name such that the moderator can give you presenter rights.

Please submit your slides at latest one day before the talk to trr257-ysr@lists.kit.edu.
Supported file format: PDF only
In the past we had bad experience when the speaker used safari and strongly recommend you to use Firefox (https://www.mozilla.org/en-US/firefox/new/).

To avoid any circumstances we recommend you to test in advance your hardware-setup using our testing area:
https://teaching.particle.kit.edu/b/mar-ysp-ekp
Access Code: <cencored (read announcement mail)>
You can start the meeting, join it automatically as presenter and upload your slides in the lower-left corner. View them by clicking on the icon in the lower-right corner.
Afterwards test your Audio/Video.

At the actual event use the URL and Access Code at the top of this information to join the event and not the url of the testing area.
You will join as "normal" user. Before your talk, the moderator will switch to your slides and assign you the virtual presenter.
If you have any questions please do not hesitate to ask.

Contact
• Tuesday, 9 June
• 14:00 16:30
Session 1 2h 30m
• Matching coefficients in nonrelativistic QCD to two-loop accuracy 15m

Nonrelativistic QCD (NRQCD) describes the system of two heavy quarks with mass $m_Q$ in the limit of small relative velocity, $v$. It is constructed by a double expansion in $\alpha_s$ and $v$ (of $1/m_Q$). In this talk we present results for various two-loop matching coefficients for operators which contribute at order $1/m_Q^2$. The results are building blocks for next-to-next-to-next-to-leading logarithmic and next-to-next-to-next-to-next-to-leading order corrections to the threshold production of top quark pairs and the decay of heavy quarkonia.

Speaker: Marvin Gerlach (KIT)
• Zero-jettiness soft and beam functions at NNLO to higher orders in epsilon 15m

We present the calculation of the next-to-next-to-leading order (NNLO) matching coefficients for all zero-jettines beam functions and the soft function through the use of master integrals, up to the second order in the dimensional-regularization parameter $\epsilon$. These higher order terms are needed for the computation of the next-to-next-to-next-to-leading order (N$^3$LO) zero-jettiness soft and beam functions.

Speaker: Daniel Baranowski (KIT)
• How to GAN LHC Events 15m

Event generation for the LHC can be supplemented by generative adversarial networks, which generate physical events and avoid highly inefficient event unweighting. For top pair production we show how such a network describes intermediate on-shell particles, phase space boundaries, and tails of distributions. In particular, we introduce the maximum mean discrepancy to resolve sharp local features. It can be extended in a straightforward manner to include for instance off-shell contributions, higher orders, or approximate detector effects.

Speaker: Ramon Winterhalder (Heidelberg U.)
• Virtual Coffee-Break 30m
• Higgs decay into a lepton pair and a photon revisited 15m

In this talk I present new calculations of the differential decay rates for $H\to \ell^+\ell^- \gamma$ with $\ell=e$ or $\mu$ in the Standard Model. The branching fractions and forward-backward asymmetries, defined in terms of the flight direction of the photon relative to the lepton momenta, depend on the cuts on energies and invariant masses of the final state particles. For typical choices of these cuts we find the branching ratios $B(H\to e \bar e \gamma)=6.1\cdot 10^{-5}$ and $B(H\to \mu \bar \mu \gamma)=6.7\cdot 10^{-5}$ and the forward-backward asymmetries $\mathcal{A}^{(e)}_{\text{FB}}=0.366$ and $\mathcal{A}^{(\mu)}_{\text{FB}}=0.280$. I also discuss contributions from different subset of diagrams and conditions for the gauge cancellation.

Speaker: Aliaksei Kachanovich (KIT)
• Searching for long lived particles from strongly interacting dark sectors 15m

LHC searches for long-lived particles typically enjoy zero background, giving strong bounds on new physics theories. At the same time, in the context of dark matter theories, long particle lifetimes can introduce interesting bounds from cosmology. In this talk, I will discuss the LHC phenomenology of long-lived particles coming from a strongly interacting dark sector, and the challenges of finding such particles if they have a low mass (of order 1-10 GeV).

Speaker: Patrick Tunney (RWTH Aachen)
• Wednesday, 17 June
• 14:00 16:30
Session 2 2h 30m
• Advances in parton branching algorithms 15m

In this talk, we will discuss a novel framework for addressing QCD factorization in the emission of multiple soft or collinear partons. The purpose of this discussion is to allow for a more precise description of hadron collider data and to better handle theoretical uncertainties from parton showers in Monte Carlo event generators. Such generators often make use of ad hoc models tuned to data e.g. to introduce azimuthal correlations between partons emitted from a hard interaction. This tuning makes the estimation of a theoretical uncertainty very difficult. We would like to avoid such constructions with our framework and pave to way for systematically going to higher orders in QCD in parton showers.

Speaker: Maximilian Löschner (KIT)
• Precision calculation of B→V form factors in QCD 15m

Applying the vacuum-to-B-meson correlation functions with an interpolating current for the light vector meson we construct the light-cone sum rules (LCSR) for the"eff ective" form factors, de ned by the corresponding hadronic matrix elements in soft-collinear e ective theory (SCET), entering the leading-power factorization formulae for QCD form factors responsible for B to V and B to V decays at large hadronic recoil at next-to-leading-order inQCD. The evanescent-operator approach for the perturbative matching of the eff ective operators from SCETI . HQET is employed in the determination of the hard-collinear functions entering the SCET factorization formulae for the vacuum-to-B-meson correlation functions. The light-quark mass eff ect for the local SCET form factors is also computed from the LCSR method with the B-meson light-cone distribution amplitude ?at O( s). Furthermore, the subleading power corrections to B to V form factors from the higher-twist B-meson light-cone distribution amplitudes are also computed with the same method at tree level up to the twist-six accuracy. Employing the two di fferent models for the B-meson light-cone distribution amplitudes consistent with QCD equations of motion, we observe that the higher-twist corrections to B to V form factors are dominated by the two-particle twist-fi ve distribution amplitude.Having at our disposal the LCSR predictions for B to V form factors, we further perform new determinations of the CKM matrix element|Vub| and predict the normalized di erential branching fractions and the q2-binned K longitudinal polarization fractions of the exclusive rare decays.

Speaker: Jing Gao (Siegen U.)
• Mixed corrections to on-shell vector boson production 15m

We report on the progress of a fully-differential description of mixed QCD-EW corrections to the production of on-shell Z and W bosons in hadronic collisions. These corrections are of phenomenological interest for the precision era of the LHC, e.g. for an improved determination of the W boson mass. We regulate soft and collinear singularities present in real emission contributions using the nested soft-collinear subtraction scheme.

Speaker: Maximilian Delto (KIT)
• Virtual Coffee-Break 30m
• Inclusive non-leptonic decays of heavy quarks: completing the $\mathcal{O}(1/m_Q^3)$ corrections 15m

We address the computation of the Darwin term contribution (1/m_b^3 correction) to the total width of the inclusive non-leptonic B meson decays, which at the quark level is originated by the transition $b \rightarrow c \bar q_1 q 2$, where $q_1 = u, c$ and $q_2 = d, s$. The key ingredients for the computation are the Heavy Quark Expansion (HQE), the optical theorem and the local expansion of the quark propagator in the external gluon field. The standard techniques of dimensional regularization and renormalization are used to deal with IR divergences. Results are obtained in the $\overline{\mbox{MS}}$ scheme.

Speaker: Daniel Moreno (Siegen U.)
• Investigation of b to u contribution to determine $V_{cb}$. 15m

We compute the moments of b to u and compare it with the software Pythia. The experimental physicists assume a relative high uncertainty for V_{cb} because of Pythia. However, we want to show that the theoretical results agree with the Monte-Carlo results very well, therefore we can minimize the uncertainty of V_{cb}.

Speaker: Muslem Rahimi (Siegen U.)
• Cornering Spontaneous CP Violation with Charged-Higgs Searches 15m

I will give a short introduction to spontaneous CP Violation and its features and discuss the role of charged Higgs searches within this framework.

Speaker: Mustafa Tabet (KIT)
• Numerical methods and beam functions at NNLO and beyond 15m

At hadron colliders, there are many interesting final states to observe. Among these, the production of color-neutral particles has gotten much attention. And indeed there are many methods to compute cross sections at NLO and NNLO. However, at NNNLO the implementation of these methods is involved. I shall present the methods to compute the soft function at NNLO which gives us the basis to compute beam functions at NNLO and ultimately at NNNLO, the last ingredient to implement to qT-slicing method at NNNLO, and report on progress that has been made so far.

Speaker: Philipp Müllender (RWTH Aachen)
• Tuesday, 23 June
• 14:00 16:30
Session 3 2h 30m
• Completing the four-body contributions to B¯ → Xsγ at NLO 15m

The inlusive radiative B¯ → Xsγ decay constitutes an important pillar in the indirect search for new physics and allows to constrain the parameter space of many models. In this talk we present the ongoing efforts in the computation of four-body contributions to the process B¯ → Xsγ, namely those of b → sqqγ ¯ at NLO in the strong coupling and the necessary complementing 5-particle cuts of the gluon-bremsstrahlung b → sqqγ ¯ + g. Although these corrections are expected to be small, this computation formally completes the NLO contributions to B¯ → Xsγ. Since the anomalous dimensions are already computed to a sufficient order, the main tasks are the systematic generation of the 1-loop amplitude, the automation of the phase space integration, the infrared-regularization and finally the renormalization of the diagrams including the operator mixing. The results obtained so far are shown and the further structure of the calculation is outlined.

Speaker: Lars-Thorben Moos (Siegen U.)
• Residual flavour symmetries: Bottom-up and top-down approaches for flavourful Leptoquarks 15m

I will first present the framework of residual flavour symmetries, which are assumed to be the residual traces of an UV flavour symmetry. In this context, bottom-up approach for reconstructing the original symmetry can be realized. In particular, we have performed a bottom-up scan for flavour-symmetries capable of addressing the SM flavour puzzle alongside of Leptoquarks patterns motivated by current flavour anomalies . Finally, I will present concrete model examples and phenomenological constraints of different leptoquarks patterns.

Speaker: Jordan Bernigaud (KIT)
• Beyond the isobar parametrization: Improving the Dalitz analysis of charmless multibody B decays 15m

The CP-violation in charmless multibody B decays is topic of ongoing discussions, as it can neither be fully explained with QCD-based methods, nor with current models. We therefore propose a model ansatz taking into account open-charm threshold effects. This parameterization naturally extends the isobar-model and is motivated by QCD-based methods. We investigate how the Dalitz-distribution and the size of CP-violation is affected by such an extension, especially when taking into account states that lie very close to the respective thresholds. In addition we argue how it can be benificial to use a different set of amplitudes in future analysis that reflect the underlying physics effects more clearly.

Speaker: Kevin Olschewsky (Siegen U.)
• Virtual Coffee-Break 30m
• Top Quark Mass Effects in Higgs Boson Production at four-loop order: Virtual Corrections 15m

We discuss the computation of finite top quark mass corrections to the four-loop Higgs boson gluon vertex and briefly recapitulate the computational methods involved.

Speaker: Florian Herren (KIT)
• Exact quark-mass dependence of the Higgs-gluon form factor at three loops in QCD 15m

We determine the three-loop form factor parameterising the amplitude for the production of an off-shell Higgs boson in gluon fusion in QCD with a single massive quark. The result is obtained via a numerical solution of a system of differential equation for the occurring master integrals. The solution is also used to determine the high-energy and threshold expansions of the form factor. Our findings may be used for the evaluation of virtual corrections generated by top-quark and b-quark loops in Higgs boson hadroproduction cross sections at next-to-next-to-leading order.

Speaker: Marco Niggetiedt (RWTH Aachen)
• Solving differential equation numerically with imaginary mass 15m

With the advancement of experimental technologies, much more precise theoretical predictions are needed in today's collider phenomenology. Computing higher order corrections to phenomenologically interesting processes often requires us to evaluate multi-loop multi-scale master integrals. In this talk I will talk about how to calculate these master integrals numerically using differential equation with respect to an additional imaginary mass parameter. Thanks to this parameter, the boundary condition of the differential equation only involves vacuum diagrams independent of masses or kinematic variables. By solving the differential equation with series expansion, we are able to calculate master integrals efficiently with arbitrary precision.

Speaker: Chen-Yu Wang (KIT)
• Functional interpolation techniques 15m

Functional interpolation techniques over fields, also known as black-box
interpolation problems, are actively studied in Computer Science for
more than a half century. Despite their probabilistic nature, they offer
a competitive alternative to purely algebraic approaches, especially
when applied over finite fields. Using the latter, one can achieve fast
and memory friendly implementations since a number swell of intermediate
expressions can be avoided. Recently, these techniques have been applied
to achieve remarkable results in the context of higher-order corrections
to scattering amplitudes. In this talk, I review functional
interpolation techniques and their implementation into the FireFly
library. I focus specifically on features helpful in the context of
integration-by-parts reductions.

Speaker: Jonas Klappert (RWTH Aachen)
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