This study showcases the approaches towards lepton identification and $γγ$ mitigation at center-of-mass energy $\sqrt{s} = 500$ GeV for semileptonic WW decays at the ILC. The analysis is performed using fully simulated Standard Model Monte Carlo events with the ILD detector concept and emphasizes the measurement of the W mass. The mass measurement is performed through the identification of a lepton and treatment of the remaining system as the hadronic W-boson. Only the most favorable beam polarization scenario for WW production is considered. The resulting detector performance benchmark obtained, with an integrated luminosity of $1600$ fb$^{-1}$ , is a statistical error on the W mass of $ΔM_{W}$ (stat.)$ = 2.4$ MeV and a relative statistical error on the WW crosssection of $Δσ/σ$(stat.)$ = 0.036\%$.
We have studied the measurement accuracy of the forward-backward asymmetry of the $e^+e^- \rightarrow t\bar{t}$ process in the 6-jet mode at $\sqrt{s} = 500$ GeV with the ILD detector. In the analysis the vertex charges of b-jets were used to distinguish t from $\bar{t}$ in each event. The distribution of the cosine of the reconstructed polar angle of so identified t or $\bar{t}$ showed a clear forward-backward asymmetry. After the correction for charge misidentification the forward-backward asymmetry was determined to be $A^t_{FB} = 0.334 \pm 0.0079$ for 500 fb$^{-1}$ with the beam polarizati…
Experimental prospects for precision observables in $e^{-}e^{+}\rightarrow q\bar{q}$ with $q=b,c$ processes at the ILC operating at 250 and 500 GeV of center of mass
The potential of measurement of the relative statistical uncertainty of the ${σ(HZ)\times BR(H \rightarrow WW^{*})}$ decay, at the International Linear Collider (ILC) has been presented. The study is performed at the lowest energy stage of the proposed staged ILC, the 250 GeV stage. Monte Carlo samples representing all SM processes were passed through full detector simulation of the International Large Detector (ILD) model. Fully hadronic final state has been analyzed using an integrated luminosity of 500 fb$^{-1}$, using multivariate analysis technique. The obtained relative statistical uncer…
The latest results on the direct experimental search for a Standard Model Higgs boson decaying to a pair of Z bosons are presented. Three distinct final states are considered: $H\rightarrow ZZ^{(*)}\rightarrow \ell\ell\ell\ell$, $H\rightarrow ZZ\rightarrow \ell\ellνν$, and $H\rightarrow ZZ\rightarrow \ell\ell qq$, where $\ell = e, μ$. A dataset of more than 1fb$^{-1}$ of proton-proton collisions at $\sqrt{s} = 7$ TeV collected by the ATLAS detector at the CERN LHC during the on-going 2011 run is used. In this model and for these final states, Higgs boson masses in the ranges 192 GeV $< m_H < $…
Searches for $B$ mesons decaying to final states containing a baryon and a lepton are performed, where the baryon is either $Λ_c$ or $Λ$ and the lepton is a muon or an electron. These decays violate both baryon and lepton number and would be a signature of physics beyond the standard model. No significant signal is observed in any of the decay modes, and upper limits in the range $(3.2-520) \times 10^{-8}$ are set on the branching fractions at the 90% confidence level.
This work presents the search for the semileptonic baryonic B decay $B^- \rightarrow Λ_c^+ \bar{p} \ell^- \barν_{\ell}$. The used data comprises the complete BABAR data set of $470 \cdot 10^{6}$ $B\bar{B}$ events, collected at the SLAC National Accelerator Laboratory. Using a pole-model decay simulation, we obtain upper limits with $90\%$ confidence level of $B(B^- \rightarrow Λ_c^+ \bar{p} e^- \barν_{e})\cdot \frac{B(Λ_c^+ \rightarrow p K^- π^+)}{5\%} < 1.2 \times 10^{-4}$, $B(B^- \rightarrow Λ_c^+ \bar{p} μ^- \barν_μ)\cdot \frac{B(Λ_c^+ \rightarrow p K^- π^+)}{5\%} < 2.5 \times 10^{-4}$, $B(…
We present a measurement of the effective weak mixing angle parameter $\sin^2θ_\text{eff}^{\ell}$, in $p\bar{p}\rightarrow Z/γ^* \rightarrow μ^+μ^-$ events at a center of mass energy of 1.96 TeV, collected by the D0 detector at the Fermilab Tevatron Collider and corresponding to 8.6 fb$^{-1}$ of integrated luminosity. The measured value of $\sin^2θ_\text{eff}^{\ell}[μμ]=0.23016 \pm 0.00064$ is further combined with the result from the D0 measurement in $p\bar{p}\rightarrow Z/γ^{*}\rightarrow e^{+} e^{-}$ events, resulting in $\sin^2θ_\text{eff}^{\ell} [\text{comb.}]=0.23095 \pm 0.00040$. This …
A search for a heavy Higgs boson in the $H\rightarrow ZZ\rightarrow 2\ell2ν$ decay channel, where $\ell$ = e or $μ$, in pp collisions at a centre-of-mass energy of 7 and 8 TeV is presented. The search is optimized separately for the vector boson fusion and the gluon fusion production processes. No significant excess is observed above the background expectation. A re-interpretation of the results as a search for an electroweak singlet extension of the Standard Model is also presented.
We report the observation of the decay $B^{-} \rightarrow D^{(*)+}_{s} K^{-} \ell^{-} \barν_{\ell}$ based on $342 \mathrm {\,fb}^{-1}}$ of data collected at the $\Y4S$ resonance with the BABAR detector at the PEP-II $e^{+}e^{-}$ storage rings at SLAC. A simultaneous fit to three $D^{+}_{s}$ decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay $B^{-} \rightarrow D^{(*)+}_{s} K^{-} \ell^{-} \barν_{\ell}$ with a significance greater than five standard deviations (including systematic uncertainties) and measu…
A measurement of the Higgs boson production cross sections via associated $WH$ and $ZH$ production using $H \rightarrow WW^{\ast} \rightarrow \ellν\ellν$ decays, where $\ell$ stands for either an electron or a muon, is presented. Results for combined $WH$ and $ZH$ production are also presented. The analysis uses events produced in proton-proton collisions collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The data correspond to an integrated luminosity of 36.1 fb$ ^{-1}$ recorded at a centre-of-mass energy of 13 TeV. The products of the $H \rightarrow WW^{\ast}$ b…
The mass of the Higgs boson is measured in the $H\rightarrow ZZ^* \rightarrow 4\ell$ and in the $H\rightarrow γγ$ decay channels with 36.1 fb$^{-1}$ of proton-proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector in 2015 and 2016. The measured value in the $H\rightarrow ZZ^* \rightarrow 4\ell$ channel is $m_{H}^{ZZ^{*}} = 124.79 \pm 0.37$ GeV, while the measured value in the $H\rightarrow γγ$ channel is $m_{H}^{γγ} = 124.93 \pm 0.40$ GeV. Combining these results with the ATLAS measurement based on 7 TeV and 8 TeV proton-proton …
The absolute branching fractions for the decays $D^-_s\!\rightarrow\!\ell^-\barν_{\ell}$ ($\ell=e$, $μ$, or $τ$) are measured using a data sample corresponding to an integrated luminosity of 521 fb$^{-1}$ collected at center of mass energies near 10.58 GeV with the \mbox{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the PEP-II $e^+e^-$ collider at SLAC. The number of $D^-_s$ mesons is determined by reconstructing the recoiling system $DKXγ$ in events of the type $e^+e^-{\rightarrow}DKXD^{*-}_s$, where $D^{*-}_s\rightarrow D^-_sγ$ and $X$ repres…
After Run 1 of the LHC, global fits to $b \rightarrow s \ell \ell$ observables show a deviation from the Standard Model (SM) with a significance of $\sim$ 4 standard devations. An example of a $b \rightarrow s \ell \ell$ process is the decay of a $B_{s}^0$ meson into two muons ($B_{s}^0 \rightarrow μ^+ μ^-$). The latest analysis of $B_{(s)}^0 \rightarrow μ^+ μ^-$ decays by LHCb with Run 1 and Run 2 data is presented. The $B_{s}^0 \rightarrow μ^+ μ^-$ decay is observed for the first time by a single experiment. In addition, the first measurement of the $B_{s}^0 \rightarrow μ^+ μ^-$ effective li…
An improved measurement of the mass of the Higgs boson is derived from a combined fit to the invariant mass spectra of the decay channels $H\rightarrow γγ$ and $H \rightarrow ZZ^{*} \rightarrow 4\ell$. The analysis uses the $pp$ collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at center-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 25 fb$^{-1}$. The measured value of the Higgs boson mass is $m_H$ = 125.36 $\pm$ 0.37 (stat) $\pm$ 0.18 (syst) GeV. This result is based on improved energy-scale calibrations for photons, el…
Results of the measurements of the 125 GeV Higgs boson properties with proton-proton collision data at $\sqrt{s}=13$ TeV collected by CMS detector are presented. The used Higgs boson decay channels include the five major decay modes, $\mathrm{H}\rightarrowγγ$, $\mathrm{H}\rightarrow{\rm Z}{\rm Z}\rightarrow4\ell$, $\mathrm{H}\rightarrow{\rm W}{\rm W}\rightarrow\ellν\ellν$, $\mathrm{H}\rightarrowτ^{+}τ^{-}$ and $\mathrm{H}\rightarrow b\bar{b}$, and two rare decay modes, $\mathrm{H}\rightarrowμ^{+}μ^{-}$ and $\mathrm{H}\rightarrow{\rm Z}/γ^{*}+γ\rightarrow\ell\ellγ$, with $\ell={\rm e},μ$. The m…
Measurements of $ZZ \rightarrow \ell\ellνν$ and $ZZjj \rightarrow \ell\ellννjj$ productions in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
We report the results of a study of the exclusive charmless semileptonic decays, $B^{+} \rightarrow η^{(\prime)} \ell^{+} ν$ and $B^{0} \rightarrow π^{-} \ell^{+} ν$, undertaken with approximately 464 million $\ensuremath{B\kern 0.18em\bar{\kern -0.18em B}}$ pairs collected at the $Υ(4S)$ resonance with the ${{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}}}$ detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions for $B^{+} \rightarrow η\ell^{+} ν…
Measurements of the total and differential cross sections of Higgs boson production are performed using 20.3 fb$^{-1}$ of $pp$ collisions produced by the Large Hadron Collider at a center-of-mass energy of $\sqrt{s} = 8$ TeV and recorded by the ATLAS detector. Cross sections are obtained from measured $H \rightarrow γγ$ and $H \rightarrow ZZ ^{*}\rightarrow 4\ell$ event yields, which are combined accounting for detector efficiencies, fiducial acceptances and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, num…
We study the processes $p\bar{p} \rightarrow WZ \rightarrow \ellν\ell^+\ell-$ and $p\bar{p} \rightarrow ZZ \rightarrow \ell^+\ell^-ν\barν, where $\ell$ = $e$ or $μ$. Using 8.6 fb$^{-1} of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider, we measure the $WZ$ production cross section to be 4.50$^{+0.63}_{-0.66} pb which is consistent with, but slightly above a prediction of the standard model. The ZZ cross section is measured to be 1.64 $\pm$ 0.46 pb, in agreement with a prediction of the standard model. Combination with an earlier analysis of the $ZZ \right…
We present a new measurement of the $WZ\rightarrow \ellν\ell\ell$ ($\ell = e,μ$) cross section and limits on anomalous triple gauge couplings. Using 4.1 fb$^{-1}$ of integrated luminosity of $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV, we observe 34 $WZ$ candidate events with an estimated background of $6.0 \pm 0.4$ events. We measure the $WZ$ production cross section to be $3.90^{+1.06}_{-0.90}$ pb, in good agreement with the standard model prediction. We find no evidence for anomalous $WWZ$ couplings and set 95% C.L. limits on the coupling parameters, $-0.075 < λ_{Z} < 0.093$ and $-0.027 …
The properties of the Higgs boson measured in bosonic decay channels ($H \rightarrow γγ$, $H \rightarrow ZZ^* \rightarrow 4\ell$, $H \rightarrow WW^{*} \rightarrow \ellν\ellν$, $H \rightarrow Zγ$) with 25 fb$^{-1}$ of pp collision data from the Large Hadron Collider run-1 collected by the ATLAS experiment are presented. The results include an improved measurement of the mass of the Higgs boson from a combined fit to the invariant mass spectra of the decay channels $H \rightarrow γγ$ and $H \rightarrow ZZ^* \rightarrow 4\ell$, which yields $m_H = 125.36 \pm 0.37$ (stat) $\pm 0.18$ (syst) GeV = …
Measurements of Higgs boson production via gluon-gluon fusion and vector-boson fusion using $H\rightarrow WW^\ast \rightarrow \ellν\ellν$ decays in $pp$ collisions with the ATLAS detector and their effective field theory interpretations
A combined measurement of differential and inclusive total cross sections of Higgs boson production is performed using 36.1 fb$^{-1}$ of 13 TeV proton-proton collision data produced by the LHC and recorded by the ATLAS detector in 2015 and 2016. Cross sections are obtained from measured $H \rightarrow γγ$ and $H \rightarrow ZZ^* \rightarrow 4\ell$ event yields, which are combined taking into account detector efficiencies, resolution, acceptances and branching fractions. The total Higgs boson production cross section is measured to be 57.0$^{+6.0}_{-5.9}$ (stat.) $^{+4.0}_{-3.3}$ (syst.) pb, in…
The quartic gauge coupling (QGC) of the electroweak interaction can be used as a probe for physics beyond the Standard Model and has been previously measured at the Large Hadron Collider. However, to achieve sensitivity to small deviations the couplings must be measured with precision beyond the capability of a hadron collider. An electron-positron collider with center-of-mass energies in the TeV range can precisely probe the QGC and test a variety of models. The International Linear Collider is such a collider project with a possible extension to $1\,$TeV. In this note the critical reconstruc…
Recent results on inclusive charmless semileptonic decays of B mesons are reviewed. Emphasis is given to measurements on the recoil of fully reconstructed B mesons, which allow to exploit several regions of phase space. Preliminary averages of the CKM matrix element $|V_{ub}|$ from the Heavy Flavour Working Group are shown, using four different theoretical calculations.
Inclusive and differential fiducial cross sections of Higgs boson production in proton-proton collisions are measured in the $H \rightarrow ZZ^* \rightarrow 4\ell$ decay channel. The proton-proton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb$^{-1}$. The inclusive fiducial cross section in the $H \rightarrow ZZ^* \rightarrow 4\ell$ decay channel is measured to be 3.62 $\pm$ 0.50 (stat) $^{+0.25}_{-0.20}$ (sys) fb, in agreement with the Stand…
An angular analysis of the decay ${\overline{B} \rightarrow D^\ast \ell^- \overlineν_\ell}$, $\ell\in\{e,μ\}$, is reported using the full $e^+e^-$ collision data set collected by the \babar experiment at the $Υ(4S)$ resonance. One $B$ meson from the ${Υ(4S)\to B\overline{B}}$ decay is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the di-lepton mass squared, $q^2$, and three angles. The first unbinned fit to the full four-dimensional decay rate i…
The future Compact Linear Collider (CLIC) offers a possibility for a rich precision physics programme, in particular in the Higgs sector through the energy staging. This is the first paper addressing the measurement of the Standard Model Higgs boson decay into two muons at 1.4 TeV CLIC. With respect to similar studies at future linear colliders, this paper includes several novel contributions to the statistical uncertainty of the measurement. The later includes the Equivalent Photon Approximation and realistic forward electron tagging based on energy deposition maps in the forward calorimeters…
The production of a prompt photon in association with a $Z$ boson is studied in proton-proton collisions at a centre-of-mass energy $\sqrt{s} =$ 13 TeV. The analysis uses a data sample with an integrated luminosity of 139 fb$^{-1}$ collected by the ATLAS detector at the LHC from 2015 to 2018. The production cross-section for the process $pp \rightarrow \ell^+\ell^-γ+X$ ($\ell = e, μ$) is measured within a fiducial phase-space region defined by kinematic requirements on the photon and the leptons, and by isolation requirements on the photon. An experimental precision of 2.9% is achieved for the…
This Letter reports a measurement of the exclusive $γγ\rightarrow \ell^+\ell^- (\ell=e, μ)$ cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV by the ATLAS experiment at the LHC, based on an integrated luminosity of $4.6$ fb$^{-1}$. For the electron or muon pairs satisfying exclusive selection criteria, a fit to the dilepton acoplanarity distribution is used to extract the fiducial cross-sections. The cross-section in the electron channel is determined to be $σ_{γγ\rightarrow e^+e^-}^{\mathrm{excl.}} = 0.428 \pm 0.035 (\mathrm{stat.}) \pm 0.018 (\mathrm{syst.})$ pb f…
This paper describes a novel algorithm for tagging jets originating from the hadronisation of strange quarks (strange-tagging) with the future International Large Detector (ILD) at the International Linear Collider (ILC). It also presents the first application of such a strange-tagger to a Higgs to strange ($h \rightarrow s\bar{s}$) analysis with the $P(e^-,e^+) = (-80\%,+30\%)$ polarisation scenario, corresponding to 900 fb$^{-1}$ of the initial proposed 2000 fb$^{-1}$ of data which will be collected by ILD during its first 10 years of data taking at $\sqrt{s} = 250$ GeV. Upper limits on the …
Dalitz decay of $K^*(892) \rightarrow K \ell^+\ell^-$: A New Probe for Hadronic Structure and Dark Photon Searches
Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Henan University of Animal Husbandry and Economy（河南牧业经济学院）；Center for High Energy Physics, Henan Academy of Sciences（河南省科学院高能物理中心）；Nanjing Normal Univerisity（南京师范大学）
We report on a study of top pair production at the International Linear Collider (ILC) around center of mass energy (E$_{\rm CM}$) = 350 GeV using an ILD detector simulator based on the Detailed Baseline Design (DBD) configuration. Here we will report on a result of 6-Jet final state, $t\ bar{t} \rightarrow bWbW \rightarrow bqqbqq$. A result for the 4-Jet final state, $t\ bar{t} \rightarrow bWbW \rightarrow bqqblν$, which has almost the same statics as that of the 6-Jet final state will be included in the future. For an energy scan of 11 center of mass energy points (340 - 350GeV) and two beam…
The $b \rightarrow s γ$, $b \rightarrow d γ$ and $b \rightarrow s \ell^+ \ell^-$ processes are allowed at higher order via the electroweak loop or box diagrams in the Standard model. It is sensitive probe to search for new physics beyond the Standard model because new particles might enter in the loop. We present preliminary results of branching fraction of the $\bar{B} \rightarrow X_s γ$, $CP$ asymmetry in the $\bar{B} \rightarrow X_{s+d} γ$, and the forward-backward asymmetry in the $\bar{B} \rightarrow X_s \ell^+ \ell^-$. The results are based on a data sample containing $772 \times 10^6 B\…
The semi-leptonic baryonic $b\to s$ decay, $Λ_b\rightarrow Λ\ell^+\ell^-$, has been studied and new angular observables and asymmetries have been proposed which can test the presence of new physics beyond the standard model.
A search for a heavy neutral Higgs boson, $A$, decaying into a $Z$ boson and another heavy Higgs boson, $H$, is performed using a data sample corresponding to an integrated luminosity of 139 fb$^{-1}$ from proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded by the ATLAS detector at the LHC. The search considers the $Z$ boson decaying into electrons or muons and the $H$ boson into a pair of $b$-quarks or $W$ bosons. The mass range considered is 230-800 GeV for the $A$ boson and 130-700 GeV for the $H$ boson. The data are in good agreement with the background predicted by the Standard Model…
Semileptonic $b \rightarrow s\ell \ell$ processes constitute a good probe for new physics phenomena: new particles contributing to the loops could affect branching fractions and angular distributions, and have different couplings to different lepton families, thus violating lepton flavour universality. Recent results from the LHCb experiment are reviewed.
$K \rightarrow π\ell^+ \ell^-$ decays, $\ell = e, μ$, will be one of the goals of future kaon facilities, like NA62 (CERN) and K$^0$TO (J-PARC). We review briefly the theoretical status of those processes.
The precision measurements of the Higgs properties is crucial for a better understanding of electroweak symmetry breaking. It can be first achieved at the ILC\pcite{Behnke2013} at $\sqrt{s}=250\rm ~GeV$ via the Higgs-strahlung production process $e^+e^-\rightarrow ZH$. The hadronic decay mode $Z\rightarrow \bar{q}q$ constitutes more than $65%$ of the total, a factor 10 more than $Z\rightarrow μμ$. An analysis based solely on the $Z$ jet pair information could thus lead to a high statistics and provide a minimum biased Higgs sample. A study of the feasibility of such analysis is shown here, bas…
The decays $\bar{B} \rightarrow D^{(*)} τ^- \barν_τ$ are good probes to new physics beyond the Standard Model. The ratios of branching fractions $R(D^{(*)}) \equiv \mathit{BF}(\bar{B} \rightarrow D^{(*)} τ^- \barν_τ) / \mathit{BF}(\bar{B} \rightarrow D^{(*)} \ell^- \barν_\ell)$ (where $\ell^- = e^-, μ^-$) measured by Belle, BaBar and LHCb show 3.9$σ$ deviation from the SM expectations as of 2015. In 2016, the Belle collaboration has shown two new measurements for the $\bar{B} \rightarrow D^{(*)} τ^- \barν_τ$ decay. These include the first application of the semileptonic tagging to the $R(D^*)$…
A search is presented for a high-mass Higgs boson in the $H\rightarrow\ell\ell\ell\ell$, $H\rightarrow\ell\ellνν$, $H\rightarrow\ell\ell qq$, and $H\rightarrowννqq$ decay modes using the ATLAS detector at the CERN Large Hadron Collider. The search uses proton-proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The results of the search are interpreted in the scenario of a heavy Higgs boson with a width that is small compared with the experimental mass resolution. The Higgs boson mass range considered extends up to 1 TeV for all…
We report a measurement of the branching fractions for $B^{0} \rightarrow π^- \ell^+ν$ and $B^{0} \rightarrow ρ^-\ell^+ν$ decays, using charged and neutral $B$ decays with isospin constraints. We find ${\cal B}(B^{0} \rightarrow π^- \ell^+ν} = (1.41 \pm 0.05 \pm 0.07) \times 10^{-4}$, and ${\cal B}(B^{0} \rightarrow ρ^-\ell^+ν} = (1.75 \pm 0.15 \pm 0.27) \times 10^{-4}$, where the first error is statistical and the second is systematic. We measure $Δ{\cal B}/Δq^2$, with 6 $q^2$ bins for $B^{0} \rightarrow π^- \ell^+ν$ and 3 \q2 bins for $B^{0} \rightarrow ρ^-\ell^+ν$, and compare the distribut…
Measurement of the total and differential Higgs boson production cross-sections at $\sqrt{s} = 13$ TeV with the ATLAS detector by combining the $H \rightarrow ZZ^* \rightarrow 4\ell$ and $H \rightarrow γγ$ decay channels
The study of flavour-changing neutral currents (FCNC) gives access to important tests of the Standard Model (SM) and allows to search for hints of beyond the SM phenomena. We present here the study of the very rare decays $B^0\rightarrow μ^+μ^-$ and $B_s^0\rightarrow μ^+μ^-$ using data corresponding to an integrated luminosity of 25 fb$^{-1}$ of $7$~TeV and $8$~TeV proton-proton collisions collected with the ATLAS detector during the LHC Run 1. For $B^0$, an upper limit on the branching fraction is set at BR$(B^0 \rightarrow μ^+μ^-) < 4.2\times 10^{-10}$ at 95\% confidence level. For $B^0_s$, …
Several recent searches for exotic and rare decays of the Standard Model Higgs boson with the ATLAS and CMS detectors are presented. The searches are performed on $\sqrt{s}$=13 TeV proton-proton collisions data collected at the LHC between 2015 and 2018. The topics covered include searches for the Higgs boson decays into two pseudoscalars, $H\rightarrow aa$, in three different final states, $2b2μ$, $4b$ and $2\mu2τ$, search for lepton-flavour violating Higgs decays, $H\rightarrow μτ/ eτ$, and search for a rare $H\rightarrow \ell\ell γ$ decay. ATLAS presents evidence for the $H\rightarrow \ell\…
This document discusses for the first time the experimental prospects on the measurement of cross section and the forward-backward asymmetry in $e^{-}e^{+}\rightarrow c\bar{c}$ collisions at 250 GeV at the International Linear Collider operating polarised beams. The cross section will be normalised to the total hadronic cross section. We discuss the results for an analysis assuming the integrated luminosity of 2000 fb$^{-1}$ foreseen in the baseline project. The measurement requires determining the charge of both jets identified as originated by a $c$-quark. The charge measurement is optimally…
The coupling properties of the Higgs boson are studied in the four-lepton decay channel using 36.1 fb$^{-1}$ of $pp$ collision data from the LHC at a centre-of-mass energy of 13 TeV collected by the ATLAS detector. Cross sections are measured for the four key production modes in several exclusive regions of the Higgs boson production phase space and are interpreted in terms of coupling modifiers. The inclusive cross section times branching ratio for $H \rightarrow ZZ^*$ decay and for a Higgs boson absolute rapidity below 2.5 is measured to be $1.73^{+0.24}_{-0.23}$(stat.)$^{+0.10}_{-0.08}$(exp…
We probe the spin ($J$) and parity ($P$) of the Standard Model Scalar (SMS) using existing searches sensitive to its production rate and kinematic properties. In particular, we search for the SMS decaying to a pair of $b$-quarks produced in association with a $W$ boson decaying leptonically. By exploiting the differences in kinematic observables, namely the transverse mass of the final state products ($M_{T}$), we attempt to distinguish between three possible $J^{P}$ hypotheses: the standard model prediction (\jpzp), a pseudoscalar (\jpzm), and a graviton-like particle (\jptp). With 9.7 fb$^{-…
Search for resonant $WZ \rightarrow \ellν\ell^{\prime}\ell^{\prime}$ production in proton$-$proton collisions at $\mathbf{\sqrt{s} = 13}$ TeV with the ATLAS detector
Composite effective field theory signal from anomalous quartic gauge couplings for $ZZ(\rightarrow\ell\ellνν)jj$ and $Zγ(\rightarrowννγ)jj$ productions
Measurement of the Higgs boson mass in the $H \rightarrow ZZ^* \rightarrow 4\ell$ decay channel using 139 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collisions recorded by the ATLAS detector at the LHC
In this paper we present results of determination of the statistical precision of Higgs branching fraction measurement, for Higgs decay to ZZ$^\ast$ pairs at 3 TeV and 350 GeV CLIC. Measurements are simulated with the CLIC_ILD detector model, taking into consideration all relevant physics and beam-induced background processes. It is shown that the product of the branching fraction BR(${H\rightarrow\thinspace ZZ^\ast}$) and the Higgs production cross-section can be measured with a relative statistical uncertainty of 3% (18%) at 3 TeV (350 GeV) center-of-mass energy, using semileptonic final sta…
We report a measurement of the branching fraction of the decay $B \rightarrow D^{(*)}π\ellν$. The analysis uses 772$\times 10^6$ $B\bar{B}$ pairs produced in $e^+e^-\rightarrow Υ(4S)$ data recorded by the Belle experiment at the KEKB asymmetric-energy $e^+e^-$ collider. The tagging $B$ meson in the decay is fully reconstructed in a hadronic decay mode. On the signal side, we reconstruct the decay $B \rightarrow D^{(*)}π\ellν$ $(\ell=e,μ)$. The measured branching fractions are $\mathcal{B}(B^+ \rightarrow D^-π^+ \ell^+ν)$ = [4.55 $\pm$ 0.27 (stat.) $\pm$ 0.39 (syst.)]$\times 10^{-3}$, $\mathcal…
At the future $e^{+}e^{-}$ linear collider ILC/CLIC it will be able to measure the photon structure functions in a wider range of kinematic variables x and $Q^{2}$ in comparison to the previous results of experiments at LEP. The classical way to measure the photon structure functions is the study of $e^{+}e^{-} \rightarrow e^{+}e^{-} γγ \rightarrow e^{+}e^{-}$ X process, where X is the leptonic or hadronic final state. For the study of the QED and hadronic photon structure functions the simulations of two-photon processes were performed at the ILC center-of-mass energy equal to 500 GeV using t…
The semitauonic decay $\bar{B} \rightarrow D^* τ^- \barν_τ$ is sensitive to new physics beyond the Standard Model (SM) that has an enhanced coupling to the $τ$ lepton. In the ratio of branching fractions $R(D^*) = \mathcal{B}(\bar{B} \rightarrow D^* τ^- \barν_τ) / \mathcal{B}(\bar{B} \rightarrow D^* \ell^- \barν_\ell)$, where $\ell^- = e^-$ or $μ^-$, a 3.3$σ$ anomaly was observed. In order to investigate the anomaly further, Belle performed a new $R(D^*)$ measurement using one-prong hadronic $τ$ decays, which was statistically independent of the previous two measurements. This measurement incl…
