Download - Positioning of IR2 collimators to intercept secondary ...EMD1: Pb Pb Pb n , Pb Pb b 96 b b G VG o 208 20882 82 208 8 2 206 Pb 8 2, 0.00485 EMD2: Pb Pb Pb 2n , 29 , 0.00970b Each of

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  • Positioning of IR2 collimators to intercept secondary beams from bound-free pair

    production and electromagnetic dissociation at the ALICE interaction point

    John Jowett

    1 J.M. Jowett, Collimation Upgrade Specification meeting, 16/3/2012

  • Ultraperipheral processes in Pb-Pb collisions

    J.M. Jowett, Collimation Upgrade Specification meeting, 16/3/2012 2

    208208 208

    2

    82 82 82

    82 82 82

    207

    08208 20

    82

    20

    8

    2082

    8 81

    08 82 82 82

    208 80

    208

    BFPP1: Pb Pb Pb e ,

    281 b, 0.01235

    BFPP2: Pb Pb Pb 2e ,

    ?? ,

    P

    0.02500

    EMD1: Pb Pb Pb n ,

    Pb

    Pb

    b

    96

    b

    b

    208208 20882 82 22 88 206 Pb

    , 0.00485

    EMD2: Pb Pb Pb 2n ,

    29 , 0.00970b

    Each of these makes a secondary beam emerging from the IP with rigidity change

    Pb1 /

    11 /

    m m

    Q Q

  • Losses during Pb-Pb Collisions in 2011

    J.M. Jowett, LHC Performance Workshop, Chamonix 7/2/2012 3

    Bound-free pair production secondary beams from IPs

    IBS & Electromagnetic dissociation at IPs, taken up by momentum collimators

    ??

    Losses from collimation inefficiency, nuclear processes in primary collimators

  • Parameters considered

    J.M. Jowett, Collimation Upgrade Specification meeting, 16/3/2012 4

    *

    6.5 TeV

    0.5 m (Nominal optics for 2019)

    Half-crossing angle 80 rady

    E Z

    p

    IP2

  • Secondary beams from Beam 1 in IR2

    J.M. Jowett, Collimation Upgrade Specification meeting, 16/3/2012 5

    Cannot separate BFPP and main beam in warm area (eg by Roman pots a la TOTEM).

  • Optimum collimator position

    J.M. Jowett, Collimation Upgrade Specification meeting, 16/3/2012 6

  • Open gap so EMD1 passes (to IR3)

    J.M. Jowett, Collimation Upgrade Specification meeting, 16/3/2012 7

    Further opening or local bumps allow other selections.

  • ATLAS and CMS ?

    ATLAS and CMS also take high-luminosity Pb-Pb

    The same problem of BFPP losses exists in the DSs around IP1 and IP5

    – Details of loss locations may be slightly different

    – Highest losses in 2011 were right of IP5

    Similar motivation to install DS collimators to avoid a peak luminosity limit from quenches and/or long-term radiation damage

    J.M. Jowett, Collimation Upgrade Specification meeting, 16/3/2012 8

  • Conclusions

    DS collimator for BFPP protection must be near Q9 in IR2

    – Unless perhaps we insert bumps?

    Detectors for BFPP ions must be located in cold section

    – Incorporate in DS collimators?

    Collimator gap can control selection of ultra-peripheral processes for physics purposes

    J.M. Jowett, Collimation Upgrade Specification meeting, 16/3/2012 9