Search

We present the first results from a proof-of-concept search for dark sectors via invisible decays of pseudoscalar η and η^{'} mesons in the NA64h experiment at the CERN SPS. Our novel technique uses the charge-exchange reaction of 50 GeV π^{-} on nuclei of an active target as the source of neutral mesons. The η,η^{'}→invisible events would exhibit themselves via a striking signature-the complete disappearance of the incoming beam energy in the detector. No evidence for such events has been found with 2.9×10^{9} pions on target accumulated during one day of data taking. This allows us to set a stringent limit on the branching ratio Br(η^{'}→invisible)<2.1×10^{-4} improving the current bound by a factor of ≃3. We also set a limit on Br(η→invisible)<1.1×10^{-4} comparable with the existing one. These results demonstrate the great potential of our approach and provide clear guidance on how to enhance and extend the sensitivity for dark sector physics from future searches for invisible neutral meson decays.

The paper considers the possibility of using the diamond-silicon carbide composite Skeleton ® with a technological coating of polycrystalline silicon as a substrate for X-ray mirrors used with powerful synchrotron radiation sources (third+ and fourth generation). Samples were studied after polishing to provide the following surface parameters: root-mean-square flatness ≃ 50 nm, micro-roughness on the frame 2 µm × 2 µm σ ≃ 0.15 nm. The heat capacity, thermal conductivity and coefficient of linear thermal expansion were investigated. For comparison, a monocrystalline silicon sample was studied under the same conditions using the same methods. The value of the coefficient of linear thermal expansion turned out to be higher than that of monocrystalline silicon and amounted to 4.3 × 10 -6  K -1 , and the values of thermal conductivity (5.0 W cm -1  K -1 ) and heat capacity (1.2 J K -1  g -1 ) also exceeded the values for Si. Thermally induced deformations of both Skeleton ® and monocrystalline silicon samples under irradiation with a CO 2 laser beam have also been experimentally studied. Taking into account the obtained thermophysical constants, the calculation of thermally induced deformation under irradiation with hard (20 keV) X-rays showed almost three times less deformation of the Skeleton ® sample than of the monocrystalline silicon sample., (open access.)

We report the first search for dark sectors performed at the NA64 experiment employing a high energy muon beam and a missing energy-momentum technique. Muons from the M2 beamline at the CERN Super Proton Synchrotron with a momentum of 160  GeV/c are directed to an active target. The signal signature consists of a single scattered muon with momentum <80  GeV/c in the final state, accompanied by missing energy, i.e., no detectable activity in the downstream calorimeters. For a total dataset of (1.98±0.02)×10^{10} muons on target, no event is observed in the expected signal region. This allows us to set new limits on the remaining (m&#95;{Z^{'}},g&#95;{Z^{'}}) parameter space of a new Z^{'} (L&#95;{μ}-L&#95;{τ}) vector boson which could explain the muon (g-2)&#95;{μ} anomaly. Additionally, our study excludes part of the parameter space suggested by the thermal dark matter relic abundance. Our results pave the way to explore dark sectors and light dark matter with muon beams in a unique and complementary way to other experiments.

Thermal dark matter models with particle χ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble interaction between the dark and ordinary matter. We report on a new search for the sub-GeV χ production through the interaction mediated by a new vector boson, called the dark photon A^{'}, in collisions of 100 GeV electrons with the active target of the NA64 experiment at the CERN SPS. With 9.37×10^{11} electrons on target collected during 2016-2022 runs NA64 probes for the first time the well-motivated region of parameter space of benchmark thermal scalar and fermionic dark matter models. No evidence for dark matter production has been found. This allows us to set the most sensitive limits on the A^{'} couplings to photons for masses m&#95;{A^{'}}≲0.35  GeV, and to exclude scalar and Majorana dark matter with the χ-A^{'} coupling α&#95;{D}≤0.1 for masses 0.001≲m&#95;{χ}≲0.1  GeV and 3m&#95;{χ}≤m&#95;{A^{'}}.

A search for a new Z^{'} gauge boson associated with (un)broken B-L symmetry in the keV-GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22×10^{11} electrons on target collected during 2016-2021 runs, no signal events were found. This allows us to derive new constraints on the Z^{'}-e coupling strength, which, for the mass range 0.3≲m&#95;{Z^{'}}≲100  MeV, are more stringent compared to those obtained from the neutrino-electron scattering data.

We performed a search for a new generic X boson, which could be a scalar (S), pseudoscalar (P), vector (V), or an axial vector (A) particle produced in the 100 GeV electron scattering off nuclei, e^{-}Z→e^{-}ZX, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such a process was found in the full NA64 dataset of 2.84×10^{11} electrons on target. We place new bounds on the S, P, V, A coupling strengths to electrons, and set constraints on their contributions to the electron anomalous magnetic moment a&#95;{e}, |Δa&#95;{X}|≲10^{-15}-10^{-13} for the X mass region 1  MeV≲m&#95;{X}≲1  GeV. These results are an order of magnitude more sensitive compared to the current accuracy on a&#95;{e} from the electron g-2 experiments and recent high-precision determination of the fine structure constant.

We report the results of a search for a new vector boson ( A ' ) decaying into two dark matter particles χ 1 χ 2 of different mass. The heavier χ 2 particle subsequently decays to χ 1 and an off-shell Dark Photon A ' ∗ → e + e - . For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay A ' → χ χ ¯ and axion-like or pseudo-scalar particles a → γ γ . With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for A ' masses from 2 m e up to 390 MeV and mixing parameter ε between 3 × 10 - 5 and 2 × 10 - 2 ., (© The Author(s) 2021.)

The gene encoding Trichoderma harzianum fungus pustulanase (ThBGL1.6, GH5 family, endo-β-1,6-glucanase, EC 3.2.1.75) was cloned and heterologously expressed by the highly productive Penicillium verruculosum fungus. The recombinant ThBGL1.6 was purified and its properties were studied. The ThBGL1.6 had an observed molecular mass of 46 kDa (SDS-PAGE data) and displayed maximum of the enzyme activity at pH 5.0 and 50 °C. At 45 °C, the ThBGL1.6 was stable for at least 3 h. The K m was 1.0 g/L with pustulan as the substrate. Reaction product analysis by HPLC clearly indicated that ThBGL1.6 has an endo-hydrolytic mode of action against pustulan as specific substrate. It was also identified that gentiobiose is the main reaction product at studying of long-term pustulan hydrolysis., (Copyright © 2020. Published by Elsevier Ltd.)

We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as a shield, and would be observed either through their a(s)→γγ decay in the rest of the HCAL detector, or as events with a large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing of the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to 2.84×10^{11} electrons on target, allowing us to set new limits on the a(s)γγ-coupling strength for a(s) masses below 55 MeV.

A novel bgl1 gene, encoding GH3 family β-glucosidase from Penicillium verruculosum (PvBGL), was cloned and heterologously expressed in P. canescens RN3-11-7 (niaD-) strain under the control of the strong xylA gene promoter. The recombinant rPvBGL was purified and their properties were studied in comparison with those of rAnBGL from Aspergillus niger expressed previously in the same fungal host. The rPvBGL had an observed molecular mass of 90 kDa (SDS-PAGE data) and displayed the enzyme maximum activity at pH 4.6 and 65 °C. The enzyme half-life time at 60 °C was found to be 87 min. Unlike the rAnBGL, the rPvBGL was not adsorbed on microcrystalline cellulose, which gives the latter enzyme an advantage in cellulose conversion with a longer time of hydrolysis., (Copyright © 2019 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

Recently, the ATOMKI experiment has reported new evidence for the excess of e + e - events with a mass ∼ 17 MeV in the nuclear transitions of 4 He, that they previously observed in measurements with 8 Be. These observations could be explained by the existence of a new vector X 17 boson. So far, the search for the decay X 17 → e + e - with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining X 17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the X 17 decay with the proposed method. To reach this goal an optimization of the X 17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [1], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate show that the goal of the proposed search is feasible., (© The Author(s) 2020.)

A search for sub-GeV dark matter production mediated by a new vector boson A^{'}, called a dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with 2.84×10^{11} electrons on target no evidence of such a process has been found. The most stringent constraints on the A^{'} mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range ≲0.2  GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search.

The gene lpmo1 encoding Penicillium verruculosum lytic polysaccharide monooxygenase (PvLPMO9A) was sequenced and homologously overexpressed in P. verruculosum B1-537 (ΔniaD) auxotrophic strain under the control of the cbh1 gene promoter in combination with either the cbh1 signal sequence (sCBH1-X series of samples) or the native lpmo1 signal sequence (sLPMO1-X series). Three enzyme samples of the sCBH1-X series were characterized by a lower overall content of cellobiohydrolases (CBHs: 26-45%) but slightly higher content of endoglucanases (EGs: 17-23%) relative to the reference B1-537 preparation (60% of CBHs and 14% of EGs), while the PvLPMO9A content in them made up 9-21% of the total secreted protein. The PvLPMO9A content in four enzyme preparations of the sLPMO1-X series was much higher (30-57%), however the portion of CBHs in most of them (except for sLPMO1-8) decreased even to a greater extent (to 21-42%) than in the samples of the sCBH1-X series. Two enzyme preparations (sCBH1-8 and sLPMO1-8), in which the content of cellulases was substantially retained and the portion of PvLPMO9A was 9-30%, demonstrated the increased yields of reducing sugars in 48-h saccharification of Avicel and milled aspen wood: 19-31 and 11-26%, respectively, compared to the reference cellulase cocktail.

The dexA gene encoding Penicillium funiculosum dextranase (GenBank accession MH581385) belonging to family 49 of glycoside hydrolases (GH49) was cloned and heterologously expressed in two recipient strains, P. canescens RN3-11-7 and P. verruculosum B1-537. Crude enzyme preparations with the recombinant dextranase content of 8-36% of the total secreted protein were obtained on the basis of new Penicillium strains. Both recombinant forms of the dextranase were isolated in a homogeneous state using chromatographic techniques. The purified enzymes displayed very similar properties, that is, pI 4.55, activity optima at pH 4.5-5.0 and 55-60 °C and a melting temperature of 60.7-60.9 °C. They were characterized by similar specific activities (1020-1340 U/mg) against dextrans with a mean molecular mass of 20, 70 and 500 kDa, as well as similar kinetic parameters in the hydrolysis of 70 kDa dextran (K m  = 1.10-1.11 g/L, k cat  = 640-680 s -1 ). However, the recombinant dextranases expressed in P. canescens and P. verruculosum had different molecular masses according to the data of SDS-PAGE (∼63 and ∼60 kDa, respectively); this was the result of different N-glycosylation patterns as MALDI-TOF mass spectrometry analysis showed. The main products of dextran hydrolysis at its initial phase were isomaltooligosaccharides, while after the prolonged time (24 h) the reaction system contained isomaltose and glucose as the major products and minor amounts of other oligosaccharides., (Copyright © 2018 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e^{+}e^{-} pairs observed in the excited ^{8}Be^{*} nucleus decays. Because of its coupling to electrons, the X could be produced in the bremsstrahlung reaction e^{-}Z→e^{-}ZX by a 100 GeV e^{-} beam incident on an active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through the subsequent decay into a e^{+}e^{-} pair. With 5.4×10^{10} electrons on target, no evidence for such decays was found, allowing us to set first limits on the X-e^{-} coupling in the range 1.3×10^{-4}≲ε&#95;{e}≲4.2×10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A^{'}) from nonobservation of the decay A^{'}→e^{+}e^{-} of the bremsstrahlung A^{'} with a mass ≲23  MeV.

Background: Penicillium verruculosum is an efficient producer of highly active cellulase multienzyme system. One of the approaches for enhancing cellulase performance in hydrolysis of cellulosic substrates is to enrich the reaction system with β -glucosidase and/or accessory enzymes, such as lytic polysaccharide monooxygenases (LPMO) displaying a synergism with cellulases., Results: Genes bglI, encoding β-glucosidase from Aspergillus niger (AnBGL), and eglIV, encoding LPMO (formerly endoglucanase IV) from Trichoderma reesei (TrLPMO), were cloned and expressed by P. verruculosum B1-537 strain under the control of the inducible gla1 gene promoter. Content of the heterologous AnBGL in the secreted multienzyme cocktails (hBGL1, hBGL2 and hBGL3) varied from 4 to 10% of the total protein, while the content of TrLPMO in the hLPMO sample was ~3%. The glucose yields in 48-h hydrolysis of Avicel and milled aspen wood by the hBGL1, hBGL2 and hBGL3 preparations increased by up to 99 and 80%, respectively, relative to control enzyme preparations without the heterologous AnBGL (at protein loading 5 mg/g substrate for all enzyme samples). The heterologous TrLPMO in the hLPMO preparation boosted the conversion of the lignocellulosic substrate by 10-43%; however, in hydrolysis of Avicel the hLPMO sample was less effective than the control preparations. The highest product yield in hydrolysis of aspen wood was obtained when the hBGL2 and hLPMO preparations were used at the ratio 1:1., Conclusions: The enzyme preparations produced by recombinant P. verruculosum strains, expressing the heterologous AnBGL or TrLPMO under the control of the gla1 gene promoter in a starch-containing medium, proved to be more effective in hydrolysis of a lignocellulosic substrate than control enzyme preparations without the heterologous enzymes. The enzyme composition containing both AnBGL and TrLPMO demonstrated the highest performance in lignocellulose hydrolysis, providing a background for developing a fungal strain capable to express both heterologous enzymes simultaneously., Competing Interests: The authors have declared that no competing interests exist.

Cellobiohydrolase I from Penicillium verruculosum (PvCel7A) has four potential N-glycosylation sites at its catalytic module: Asn45, Asn194, Asn388, and Asn430. In order to investigate how the N-glycosylation influences the activity and other properties of the enzyme, the wild type (wt) PvCel7A and its mutant forms, carrying Asn to Ala substitutions, were cloned into Penicillium canescens PCA10 (niaD-) strain, a fungal host for production of heterologous proteins. The rPvCel7A-wt and N45A, N194A, N388A mutants were successfully expressed and purified for characterization, whereas the expression of N430A mutant was not achieved. The MALDI-TOF mass spectrometry fingerprinting of peptides, obtained as a result of digestion of rPvCel7A forms with specific proteases, showed that the N-linked glycans represent variable high-mannose oligosaccharides and the products of their sequential enzymatic trimming, according to the formula (Man)0-13 (GlcNAc)2 , or a single GlcNAc residue. Mutations had no notable effect on pH-optimum of PvCel7A activity and enzyme thermostability. However, the mutations influenced both the enzyme adsorption ability on Avicel and its activity against natural and synthetic substrates. In particular, the N45A mutation led to a significant increase in the rate of Avicel and milled aspen wood hydrolysis, while the substrate digestion rates in the case of N194A and N388A mutants were notably lower relative to rPvCel7A-wt. These data, together with data of 3D structural modeling of the PvCel7A catalytic module, indicate that the N-linked glycans are an important part of the processive catalytic machinery of PvCel7A., (© 2015 Wiley Periodicals, Inc.)

Two glucoamylases, a recombinant enzyme from Penicillium verruculosum (PvGla) heterologously expressed in Penicillium canescens RN3-11-7 (niaD-) strain and a native glucoamylase from Myceliophthora thermophila (MtGla), were purified and their properties were studied. MtGla displayed 2-5-fold higher specific activities against soluble starch, amylose and amylopectin than PvGla. MtGla also provided higher glucose yields in extended hydrolysis of the polymeric substrates. Analysis of 3D model structures of the intact PvGla and MtGla, which were built using the 2vn7.pdb crystal structure of the intact Trichoderma reesei glucoamylase (TrGla) as a template, showed that the reason for lower hydrolytic performance of PvGla in comparison to MtGla may be less strong interactions between the enzyme domains as well as a longer (by 17 residues) linker in the first enzyme., (Copyright © 2015 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

Penicillium canescens is a filamentous fungus that normally does not secrete notable levels of cellulase activity. Cellobiohydrolase I of P. canescens (PcCel7A) was homologously cloned into a host strain RN3-11-7 (niaD-) and then expressed under the control of a strong xylA promoter. Using three steps of chromatography, PcCel7A was purified. The enzyme displayed maximum activity at pH 4.0-4.5. PcCel7A was stable at 50°C and pH 4.5 at least for 3h, while at 60°C it lost 45% of activity after 30min of incubation. When equalized by protein concentration, PcCel7A demonstrated a higher performance in prolonged hydrolysis of Avicel and milled aspen wood than CBH I (Cel7A) from Trichoderma reesei, the most industrially utilized cellulase at this moment. The high catalytic efficiency of the PcCel7A makes it a potential candidate for industrial applications., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Objective: To report the analysis of 3 cases of ancient trepanation discovered in the craniological collection (153 skulls) of the Pazyryk nomadic culture (500-300 bc) from the Gorny Altai, Russia, and to evaluate the technique, instrumentation, and materials used for cranial surgery as well as the motivation for the trepanations in Scythian times., Methods: A multidisciplinary approach was chosen to study the trepanned skulls. Visual inspection and examination under magnification, multislice computed tomography, high-field magnetic resonance imaging, and coupled plasma mass spectrometry and synchrotron radiation-induced x-ray fluorescence analysis of the bone samples from the site of trephination were used., Results: In the Pazyryk culture, trepanation was very likely used to perform the intracranial procedures that were not yet indicated by Hippocrates. No signs of bone infection were detected. Higher copper abundance found at the site of trepanation showed that a bronze knife was the most likely tool used by Scythian surgeons., Conclusions: Our data suggest that the Scythian population of the Altai Mountains had sufficient medical knowledge to perform sophisticated and successful manipulations on the human skulls. Scraping technique with bronze tools was quite effective for prevention of wound infection and resulted in a high survival rate after surgery. In the era of methicillin-resistant Staphylococcus aureus, it may be useful to consider some ancient surgical technologies., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Here we report the first isolation to homogeneous forms of two glucoamylases from the fungus Penicillium verruculosum and their study in comparison with known glucoamylases from Aspergillus awamori and Aspergillus niger. Genes that encode glucoamylases from P. verruculosum were cloned and expressed in the fungus Penicillium canescens, and the recombinant glucoamylases were obtained with subsequent study of their molecular weights, isoelectric points, optimal temperature and pH values, and stability. The catalytic activities of the recombinant glucoamylases were determined in relation to soluble potato starch. Changes in molecular mass distribution and content of low molecular weight products during starch hydrolysis by glucoamylases from P. verruculosum, A. awamori, and A. niger were studied. An exo-depolymerization mechanism was established to be the pathway for destruction of starch by the glucoamylases.

The genes inuA and inu1, encoding two inulinases (32nd glycosyl hydrolase family) from filamentous fungi Aspergillus niger and A. awamori, were cloned into Penicillium canescens recombinant strain. Using chromatographic techniques, endoinulinase InuA (56 kDa, pI 3) and exoinulinase Inu1 (60 kDa, pI 4.3) were purified to homogeneity from the enzymatic complexes of P. canescens new transformants. The properties, such as substrate specificity, pH- and T-optima of activity, stability at different temperatures, influence of cations and anions on the catalytic activity, etc., of both recombinant inulinases were studied.

An enzyme preparation has been produced on the basis of Penicillium canescens strains with the activity of cellibiohydrolase I, II; endo-1,4-beta-gluconase of Penicillium verruculosum; and beta-glucosidase of Aspergillus niger. It was shown that for the most effective hydrolysis of aspen wood pulp the optimal ratio of cellobiohydrolase and endo- 1,4-3-gluconase in enzyme preparations was 8 : 2 (by protein). It was also established that the homologous xylanase secreted by the Penicillium canescens fungus is a required component for the enzyme complex for hydrolysis of the hemicellulose matrix of aspen wood.