Core excitations across the neutron shell gap in 207 Tl

The single closed-neutron-shell, one proton–hole nucleus 207 Tl was populated in deep-inelastic collisions of a 208 Pb beam with a 208 Pb target. The yrast and near-yrast level scheme has been established up to high excitation energy, comprising an octupole phonon state and a large number of core excited states. Based on shell-model calculations, all observed single core excitations were established to arise from the breaking of the N=126 neutron core. While the shell-model calculations correctly predict the ordering of these states, their energies are compressed at high spins. It is concluded that this compression is an intrinsic feature of shell-model calculations using two-body matrix elements developed for the description of two-body states, and that multiple core excitations need to be considered in order to accurately calculate the energy spacings of the predominantly three-quasiparticle states

The pMSSM10 after LHC run 1

We present a frequentist analysis of the parameter space of the pMSSM10, in which the following ten soft SUSY-breaking parameters are specified independently at the mean scalar top mass scale MSUSY≡mt~1mt~2 : the gaugino masses M1,2,3 , the first-and second-generation squark masses mq~1=mq~2 , the third-generation squark mass mq~3 , a common slepton mass mℓ~ and a common trilinear mixing parameter A , as well as the Higgs mixing parameter μ , the pseudoscalar Higgs mass MA and tanβ , the ratio of the two Higgs vacuum expectation values. We use the MultiNest sampling algorithm with ∼ 1.2 ×109 points to sample the pMSSM10 parameter space. A dedicated study shows that the sensitivities to strongly interacting sparticle masses of ATLAS and CMS searches for jets, leptons + signals depend only weakly on many of the other pMSSM10 parameters. With the aid of the Atom and Scorpion codes, we also implement the LHC searches for electroweakly interacting sparticles and light stops, so as to confront the pMSSM10 parameter space with all relevant SUSY searches. In addition, our analysis includes Higgs mass and rate measurements using the HiggsSignals code, SUSY Higgs exclusion bounds, the measurements of BR(Bs→μ+μ-) by LHCb and CMS, other B -physics observables, electroweak precision observables, the cold dark matter density and the XENON100 and LUX searches for spin-independent dark matter scattering, assuming that the cold dark matter is mainly provided by the lightest neutralino χ~10 . We show that the pMSSM10 is able to provide a supersymmetric interpretation of (g-2)μ , unlike the CMSSM, NUHM1 and NUHM2. As a result, we find (omitting Higgs rates) that the minimum χ2=20.5 with 18 degrees of freedom (d.o.f.) in the pMSSM10, corresponding to a χ2 probability of 30.8 %, to be compared with χ2/d.o.f.=32.8/24(31.1/23)(30.3/22) in the CMSSM (NUHM1) (NUHM2). We display the one-dimensional likelihood functions for sparticle masses, and we show that they may be significantly lighter in the pMSSM10 than in the other models, e.g., the gluino may be as light as ∼ 1250 GeV at the 68 % CL, and squarks, stops, electroweak gauginos and sleptons may be much lighter than in the CMSSM, NUHM1 and NUHM2. We discuss the discovery potential of future LHC runs, e+e- colliders and direct detection experiments

The NUHM2 after LHC Run 1

We make a frequentist analysis of the parameter space of the NUHM2, in which the soft supersymmetry (SUSY)-breaking contributions to the masses of the two Higgs multiplets, mHu,d2 , vary independently from the universal soft SUSY-breaking contributions m02 to the masses of squarks and sleptons. Our analysis uses the MultiNest sampling algorithm with over 4×108 points to sample the NUHM2 parameter space. It includes the ATLAS and CMS Higgs mass measurements as well as the ATLAS search for supersymmetric jets +  /ET signals using the full LHC Run 1 data, the measurements of BR(Bs→μ+μ-) by LHCb and CMS together with other B-physics observables, electroweak precision observables and the XENON100 and LUX searches for spin-independent dark-matter scattering. We find that the preferred regions of the NUHM2 parameter space have negative SUSY-breaking scalar masses squared at the GUT scale for squarks and sleptons, m02<0 , as well as mHu2<mHd2<0 . The tension present in the CMSSM and NUHM1 between the supersymmetric interpretation of (g-2)μ and the absence to date of SUSY at the LHC is not significantly alleviated in the NUHM2. We find that the minimum χ2=32.5 with 21 degrees of freedom (dof) in the NUHM2, to be compared with χ2/dof=35.0/23 in the CMSSM, and χ2/dof=32.7/22 in the NUHM1. We find that the one-dimensional likelihood functions for sparticle masses and other observables are similar to those found previously in the CMSSM and NUHM1

hhjj production at the LHC

The search for di-Higgs production at the LHC in order to set limits on the Higgs trilinear coupling and constraints on new physics is one of the main motivations for the LHC high-luminosity phase. Recent experimental analyses suggest that such analyses will only be successful if information from a range of channels is included. We therefore investigate di-Higgs production in association with two hadronic jets and give a detailed discussion of both the gluon- and the weak boson-fusion (WBF) contributions, with a particular emphasis on the phenomenology with modified Higgs trilinear and quartic gauge couplings. We perform a detailed investigation of the full hadronic final state and find that hhjj production should add sensitivity to a di-Higgs search combination at the HL-LHC with 3 ab-1 . Since the WBF and GF contributions are sensitive to different sources of physics beyond the Standard Model, we devise search strategies to disentangle and isolate these production modes. While gluon fusion remains non-negligible in WBF-type selections, sizeable new physics contributions to the latter can still be constrained. As an example of the latter point we investigate the sensitivity that can be obtained for a measurement of the quartic Higgs–gauge boson couplings

Collectivity in A ∼ 70 nuclei studied via lifetime measurements in 70 Br and 68,70 Se

Transition strengths for decays from low-lying states in A ∼ 70 nuclei have been deduced from lifetime measurements using the recoil distance Doppler shift technique. The results confirm the collectivity previously reported for the <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mrow><mn>2</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mo stretchy="false">→</mo><msubsup><mrow><mn>0</mn></mrow><mrow><mi mathvariant="italic">gs</mi></mrow><mrow><mo>+</mo></mrow></msubsup></math> decay in 68 Se and reveal a relative decrease in collectivity in 70 Br. This trend is reproduced by shell model calculations using the GXPF1A interaction in an fp model space including the Coulomb, spin-orbit and isospin non-conserving interactions. The <math altimg="si2.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mrow><mn>3</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mo stretchy="false">→</mo><msubsup><mrow><mn>2</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math> decay in 70 Br is found to have a very small B(M1) value, which is consistent with the configuration of the state being dominated by the coupling of <math altimg="si3.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>f</mi></mrow><mrow><mfrac><mn>5</mn><mn>2</mn></mfrac></mrow></msub></math> protons and neutrons. The results suggest that the <math altimg="si4.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>g</mi></mrow><mrow><mfrac><mn>9</mn><mn>2</mn></mfrac></mrow></msub></math> orbit does not play an important role at low spin in these nuclei. The B(E2) values for the decays of the (T = 1) <math altimg="si5.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mrow><mn>2</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math> states in 70 Br and 70 Se are almost identical, suggesting there is no major shape change between the two nuclei at low spin

Next-to-leading order QCD predictions for top-quark pair production with up to two jets merged with a parton shower

We present differential cross sections for the production of top-quark pairs in conjunction with up to two jets, computed at next-to-leading order in perturbative QCD and consistently merged with a parton shower in the S herpa +O pen L oops framework. Top quark decays including spin correlation effects are taken into account at leading order accuracy. The calculation yields a unified description of top-pair plus multi-jet production, and detailed results are presented for various key observables at the Large Hadron Collider. A large improvement with respect to the multi-jet merging approach at leading order is found for the total transverse energy spectrum, which plays a prominent role in searches for physics beyond the Standard Model

Review of lattice results concerning low-energy particle physics

We review lattice results related to pion, kaon D - and B -meson physics with the aim of making them easily accessible to the particle-physics community. More specifically, we report on the determination of the light-quark masses, the form factor f+(0) arising in semileptonic K→π transition at zero momentum transfer, as well as the decay-constant ratio fK/fπ of decay constants and its consequences for the CKM matrix elements Vus and Vud . Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2)L×SU(2)R and SU(3)L×SU(3)R Chiral Perturbation Theory and review the determination of the BK parameter of neutral kaon mixing. The inclusion of heavy-quark quantities significantly expands the FLAG scope with respect to the previous review. Therefore, we focus here on D - and B -meson decay constants, form factors, and mixing parameters, since these are most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. In addition we review the status of lattice determinations of the strong coupling constant αs

Bose–Einstein correlations in hadron-pairs from lepto-production on nuclei ranging from hydrogen to xenon

Bose–Einstein correlations of like-sign charged hadrons produced in deep-inelastic electron and positron scattering are studied in the HERMES experiment using nuclear targets of 1 H, 2 H, 3 He, 4 He, N, Ne, Kr, and Xe. A Gaussian approach is used to parametrize a two-particle correlation function determined from events with at least two charged hadrons of the same sign charge. This correlation function is compared to two different empirical distributions that do not include the Bose–Einstein correlations. One distribution is derived from unlike-sign hadron pairs, and the second is derived from mixing like-sign pairs from different events. The extraction procedure used simulations incorporating the experimental setup in order to correct the results for spectrometer acceptance effects, and was tested using the distribution of unlike-sign hadron pairs. Clear signals of Bose–Einstein correlations for all target nuclei without a significant variation with the nuclear target mass are found. Also, no evidence for a dependence on the invariant mass W of the photon-nucleon system is found when the results are compared to those of previous experiments

Spin density matrix elements in exclusive ω electroproduction on 1 H and 2 H targets at 27.5 GeV beam energy

Exclusive electroproduction of <math><mi mathvariant="italic">ω</mi></math> mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of <math><mrow><msup><mi>Q</mi><mn>2</mn></msup><mo>&gt;</mo><mn>1.0</mn></mrow></math>  GeV <math><msup><mrow/><mn>2</mn></msup></math> , 3.0 GeV  <math><mrow><mo>&lt;</mo><mi>W</mi><mo>&lt;</mo></mrow></math>  6.3 GeV, and <math><mrow><mo>-</mo><msup><mi>t</mi><mo>′</mo></msup><mo>&lt;</mo><mn>0.2</mn></mrow></math>  GeV <math><msup><mrow/><mn>2</mn></msup></math> . Results on the angular distribution of the <math><mi mathvariant="italic">ω</mi></math> meson, including its decay products, are presented. The data were accumulated with the HERMES forward spectrometer during the 1996–2007 running period using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. The determination of the virtual-photon longitudinal-to-transverse cross-section ratio reveals that a considerable part of the cross section arises from transversely polarized photons. Spin density matrix elements are presented in projections of <math><msup><mi>Q</mi><mn>2</mn></msup></math> or <math><mrow><mo>-</mo><msup><mi>t</mi><mo>′</mo></msup></mrow></math> . Violation of <math><mi>s</mi></math> -channel helicity conservation is observed for some of these elements. A sizable contribution from unnatural-parity-exchange amplitudes is found and the phase shift between those amplitudes that describe transverse <math><mi mathvariant="italic">ω</mi></math> production by longitudinal and transverse virtual photons, <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>L</mi><mrow><mrow/><mo>∗</mo></mrow></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>T</mi></msub></mrow></math> and <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>T</mi><mrow><mrow/><mo>∗</mo></mrow></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>T</mi></msub></mrow></math> , is determined for the first time. A hierarchy of helicity amplitudes is established, which mainly means that the unnatural-parity-exchange amplitude describing the <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>T</mi><mo>∗</mo></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>T</mi></msub></mrow></math> transition dominates over the two natural-parity-exchange amplitudes describing the <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>L</mi><mo>∗</mo></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>L</mi></msub></mrow></math> and <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>T</mi><mo>∗</mo></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>T</mi></msub></mrow></math> transitions, with the latter two being of similar magnitude. Good agreement is found between the HERMES proton data and results of a pQCD-inspired phenomenological model that includes pion-pole contributions, which are of unnatural parity

Measurement of multijet production in ep collisions at high Q2 and determination of the strong coupling αs

Inclusive jet, dijet and trijet differential cross sections are measured in neutral current deep-inelastic scattering for exchanged boson virtualities 150<Q2<15000GeV2 using the H1 detector at HERA. The data were taken in the years 2003 to 2007 and correspond to an integrated luminosity of 351pb-1 . Double differential Jet cross sections are obtained using a regularised unfolding procedure. They are presented as a function of Q2 and the transverse momentum of the jet, PTjet , and as a function of Q2 and the proton’s longitudinal momentum fraction, ξ , carried by the parton participating in the hard interaction. In addition normalised double differential jet cross sections are measured as the ratio of the jet cross sections to the inclusive neutral current cross sections in the respective Q2 bins of the jet measurements. Compared to earlier work, the measurements benefit from an improved reconstruction and calibration of the hadronic final state. The cross sections are compared to perturbative QCD calculations in next-to-leading order and are used to determine the running coupling and the value of the strong coupling constant as αs(MZ)=0.1165(8)exp(38)pdf,theo