A search for the electroweak production of a vector-like quark T′, decaying to a top quark and a Higgs boson is presented. The search is based on a sample of proton-proton collision events recorded at the LHC at   <math> <msqrt> <mi>s</mi> </msqrt> </math>  $$ \sqrt{s} $$  = 13 TeV, corresponding to an integrated luminosity of 138 fb −1. This is the first T′ search that exploits the Higgs boson decay to a pair of photons. For narrow isospin singlet T′ states with masses up to 1.1 TeV, the excellent diphoton invariant mass resolution of 1–2% results in an increased sensitivity compared to previous searches based on the same production mechanism. The electroweak production of a T′ quark with mass up to 960 GeV is excluded at 95% confidence level, assuming a coupling strength κ T = 0.25 and a relative decay width Γ/M T′ &lt; 5%.

Armenia

A. Tumasyan

Austria

W. Adam

J. Andrejkovic

T. Bergauer

S. Chatterjee

K. Damanakis

M. Dragicevic

A. Escalante Del Valle

P. Hussain

M. Jeitler

N. Krammer

L. Lechner

D. Liko

I. Mikulec

P. Paulitsch

F. Pitters

J. Schieck

R. Schöfbeck

D. Schwarz

M. Sonawane

S. Templ

W. Waltenberger

C.E. Wulz

Belgium

Egypt

M. Darwish

T. Janssen

T. Kello

H. Rejeb Sfar

P. Mechelen

E. Bols

J. D’Hondt

A. Moor

M. Delcourt

H. Faham

S. Lowette

S. Moortgat

A. Morton

D. Müller

A. Sahasransu

S. Tavernier

W. Doninck

D. Vannerom

B. Clerbaux

G. Lentdecker

L. Favart

D. Hohov

J. Jaramillo

K. Lee

M. Mahdavikhorrami

I. Makarenko

A. Malara

S. Paredes

L. Pétré

N. Postiau

L. Thomas

M. Bemden

C. Vander Velde

P. Vanlaer

D. Dobur

J. Knolle

L. Lambrecht

G. Mestdach

C. Rendón

A. Samalan

K. Skovpen

M. Tytgat

N. Bossche

B. Vermassen

L. Wezenbeek

A. Benecke

G. Bruno

F. Bury

C. Caputo

P. David

C. Delaere

I. Donertas

A. Giammanco

K. Jaffel

Sa. Jain

V. Lemaitre

K. Mondal

A. Taliercio

T. Tran

P. Vischia

S. Wertz

Brazil

G. Alves

E. Coelho

C. Hensel

A. Moraes

P. Rebello Teles

W. Aldá Júnior

M. Alves Gallo Pereira

M. Barroso Ferreira Filho

H. Brandao Malbouisson

W. Carvalho

J. Chinellato

E. Costa

G. Silveira

D. De Jesus Damiao

V. Dos Santos Sousa

S. Fonseca De Souza

Search for a vector-like quark T′ → tH via the diphoton decay mode of the Higgs boson in proton-proton collisions at   <math> <msqrt> <mi>s</mi> </msqrt> </math>  $$ \sqrt{s} $$  = 13 TeV

The charge-parity (CP) structure of the Yukawa interaction between the Higgs (H) boson and the top quark is measured in a data sample enriched in the t  <math> <mover> <mi>t</mi> <mo>¯</mo> </mover> </math>  $$ \overline{\textrm{t}} $$ H and tH associated production, using 138 fb −1 of data collected in proton-proton collisions at   <math> <msqrt> <mi>s</mi> </msqrt> </math>  $$ \sqrt{s} $$  = 13 TeV by the CMS experiment at the CERN LHC. The study targets events where the H boson decays via H → WW or H → ττ and the top quarks decay via t → Wb: the W bosons decay either leptonically or hadronically, and final states characterized by the presence of at least two leptons are studied. Machine learning techniques are applied to these final states to enhance the separation of CP -even from CP -odd scenarios. Two-dimensional confidence regions are set on κ t and   <math> <mover> <mi>κ</mi> <mo>~</mo> </mover> </math>  $$ \overset{\sim }{\kappa } $$  t, which are respectively defined as the CP -even and CP -odd top-Higgs Yukawa coupling modifiers. No significant fractional CP -odd contributions, parameterized by the quantity |   <math> <msubsup> <mi>f</mi> <mi>CP</mi> <mi>Htt</mi> </msubsup> </math>  $$ {f}_{CP}^{\textrm{Htt}} $$  | are observed; the parameter is determined to be |   <math> <msubsup> <mi>f</mi> <mi>CP</mi> <mi>Htt</mi> </msubsup> </math>  $$ {f}_{CP}^{\textrm{Htt}} $$  | = 0.59 with an interval of (0.24, 0.81) at 68% confidence level. The results are combined with previous results covering the H → ZZ and H → γγ decay modes, yielding two- and one-dimensional confidence regions on κ t and   <math> <mover> <mi>κ</mi> <mo>~</mo> </mover> </math>  $$ \overset{\sim }{\kappa } $$  t, while |   <math> <msubsup> <mi>f</mi> <mi>CP</mi> <mi>Htt</mi> </msubsup> </math>  $$ {f}_{CP}^{\textrm{Htt}} $$  | is determined to be |   <math> <msubsup> <mi>f</mi> <mi>CP</mi> <mi>Htt</mi> </msubsup> </math>  $$ {f}_{CP}^{\textrm{Htt}} $$  | = 0.28 with an interval of |   <math> <msubsup> <mi>f</mi> <mi>CP</mi> <mi>Htt</mi> </msubsup> </math>  $$ {f}_{CP}^{\textrm{Htt}} $$  | &lt; 0.55 at 68% confidence level, in agreement with the standard model CP -even prediction of |   <math> <msubsup> <mi>f</mi> <mi>CP</mi> <mi>Htt</mi> </msubsup> </math>  $$ {f}_{CP}^{\textrm{Htt}} $$  | = 0.

E. Starling

M. Niedziela

C. Roskas

J. Prisciandaro

Search for CP violation in t  <math> <mover> <mi>t</mi> <mo>¯</mo> </mover> </math>  $$ \overline{\textrm{t}} $$ H and tH production in multilepton channels in proton-proton collisions at   <math> <msqrt> <mi>s</mi> </msqrt> </math>  $$ \sqrt{s} $$  = 13 TeV

$^{232}$Th/$^{233}$U fuel cycle is an alternate candidate for future nuclear energy. Neutron-induced fission cross section of $^{232}$Th is one of the important nuclear data if using thorium as the fuel in the future. $^{232}$Th(n, f) cross sections from 1 to 300 MeV were measured at China Spallation Neutron Source (CSNS) Back-streaming neutron facility (Back-n) relative to $^{235}$U(n, f) and n-p scattering. A fast ionization chamber for fission cross section measurement (FIXM) and a proton recoil telescope (PRT) were used to perform the measurement. The neutron energy in this measurement reaches up to 300 MeV which is supposed to be the highest among the current Experimental Nuclear Reaction Data (EXFOR) library. It stands as the only experimental data in the region of 200-300 MeV in EXFOR as well. The experimental and evaluated data of $^{232}$Th(n, f) cross section above 60 MeV are scarce, the measurement data of this work will be valuable references for future evaluation in high energy. For the data below 60 MeV, most of our data are more consistent with ENDF/B-VIII.0, excepting in the region of 1-2 MeV where our data are more in favor of CENDL-3.2.

China

Yonghao Chen

Yiwei Yang

Zhizhou Ren

Wei Jiang

Ruirui Fan

Han Yi

Rong Liu

Jingyu Tang

Hantao Jing

Yang Li

Qiang Li

Zhixin Tan

Qi An

Jiangbo Bai

Jie Bao

Yu Bao

Ping Cao

Haolei Chen

Qiping Chen

Zhen Chen

Zengqi Cui

Changqing Feng

Keqing Gao

Xiaolong Gao

Minhao Gu

Changcai Han

Zijie Han

Guozhu He

Yongcheng He

Yang Hong

Yiwei Hu

Hanxiong Huang

Xiru Huang

Haoyu Jiang

Zhijie Jiang

Ling Kang

Bo Li

Chao Li

Jiawen Li

Xiao Li

Jie Liu

Shubin Liu

Xingyan Liu

Ze Long

Guangyuan Luan

Changjun Ning

Mengchen Niu

Binbin Qi

Jie Ren

Xichao Ruan

Zhaohui Song

Kang Sun

Zhijia Sun

Xinyi Tang

Binbin Tian

Lijiao Wang

Pengcheng Wang

Zhaohui Wang

Zhongwei Wen

Xiaoguang Wu

Xuan Wu

Likun Xie

Xiaoyun Yang

Li Yu

Tao Yu

Yongji Yu

Guohui Zhang

Linhao Zhang

Qiwei Zhang

Xianpeng Zhang

Yuliang Zhang

Zhiyong Zhang

Luping Zhou

Zhihao Zhou

Kejun Zhu

Measurement of neutron-induced fission cross sections of Th from 1 to 300 MeV at CSNS Back-n

We derive all-order expressions for perturbations of the Einstein-Hilbert action and the Einstein equation with the general n-th order terms. To this end, we employ Cheung and Remmen’s perturbation conventions both in tensor density and the usual metric tensor formalisms, including the Einstein-dilaton theory. Remarkably, we find minimal building blocks that generate the entire perturbations for each of our formulations. We show that the number of terms of perturbations grows linearly as the order of perturbations increases. We regard our results as the reference and discuss how to derive perturbations in other conventions from the reference. As a consistency check, we compute graviton scattering amplitudes using the perturbiner method based on the perturbative Einstein equation. Finally we discuss how to generalise the results to curved backgrounds and incorporate additional matter.

South Korea

Kyoungho Cho

Kwangeon Kim

Kanghoon Lee

Perturbations of general relativity to all orders and the general n th order terms

Relative isotopic yield distributions have been extracted for nine correlated fission fragment pairs following a detailed analysis of prompt <math><mi>γ</mi><mo>−</mo><mi>γ</mi></math> coincidence events from $^{232}$Th(α,f) reaction at E<math><msub><mrow></mrow><mrow><mi>l</mi><mi>a</mi><mi>b</mi></mrow></msub></math> = 30 MeV. Simultaneously, the charge and mass yield distributions of the even-even fission fragments have been obtained from the measured relative isotopic yields. The onset of a triple-hump structure is seen in the extracted charge as well as mass yield distributions of the fragments. The results are consistent with the two-mode fission hypothesis of compound nucleus and in good agreement with the theoretical predictions, based on relevant fission models. The detailed results provide experimental evidence for the presence of two distinct compound nucleus fission modes, where the asymmetric and symmetric fission components are 83% and 17%, respectively. An average neutron multiplicity value of 4.60 ± 0.09 has been obtained, and the extracted neutron multiplicity distribution pattern corroborates the observed features of the multifaceted fission modes. Comparing the measured yield distributions following the $^{232}$Th(α,f) surrogate reaction, which produces $^{236}$U$^{⁎}$ at an excitation energy of 21.5 MeV, with that of the direct reaction of 14 MeV neutron induced fission of $^{235}$U, an increase of about 11% in the yield of the symmetric component has been observed.

India

Aniruddha Dey

D.C. Biswas

Evidence for competing bi-faceted compound nucleus fission modes in Th( ,f) Reaction